The operation includes testing the ore, sampling and pulverizing, weighing the ore and reagents, calcination and roasting, reduction and fusion, distillation and sublimation, scorification and cupellation, inquartation and parting the gold and silver, weighing and tabulating. "Notes on Assaying" by Dr. Ricketts is a very useful manual to have at hand.

A TOLERABLY COMPLETE OUTFIT INCLUDES:

A pair of scales for weighing ore and buttons of base metal. It should take 10 ounces in each pan, and show 1/20 of a grain.

A bullion scale to be kept strictly for the precious metals. Loaded with one gramme, it should show 1/20 of a milligramme.

Weights. Avoirdupois; troy, metric and "assay." Assay weights save much calculation. The unit of the system is a weight of 29.166 grammes. Its derivation is as follows:

2000 lbs. : 1 A.T. :: 1 oz. Troy : 1 milligramme.

To use this system, weigh out one A.T. of the ore and whatever number of milligrammes of gold and silver the assay gives indicates an equal number of Troy ounces to the ton of 2000 lbs. Avoirdupois.

A muffle and a melting furnace, portable and of medium size, are handy, though furnaces may be built of ordinary brick, lined with fire brick, that would be better for permanent use.

The fuels may be coke, anthracite or bituminous coal, charcoal, oil or gas.

Crucibles of black lead, French clay, Hessian sand, and quicklime are necessary to hold the assay.

Roasting dishes, scorifiers and cupels are required. The cupel is made of the ashes of burnt bone, and it is better to make them on the spot, as the bone ash may be carried anywhere without damage, whereas the cupels are very fragile. The bone ash is moistened with water, stamped in a cupel mould, and allowed to dry slowly. A good one will absorb its own weight of lead, but it is better to calculate on its absorbing but three-quarters of that amount.

The crucible, scorification and cupel tongs, a couple of hammers, iron pestle and mortar, sieves from 20 to 100 mesh, and scorification mould complete the requisite tools.

In addition, however, the assayer will require quite a bulky lot of apparatus, reagents and chemicals. All dealers keep lists of assayers' supplies on hand, and a full and complete assortment will cost about $200 in New York or Chicago. Quart bottles, with glass stoppers; ordinary corked bottles, ring stands, alcohol lamps, wash bottles, test tubes, horn spoons, iron pans, parting flasks, annealing cups, glazed black paper—these will suffice, provided the assayer has, as well, the outfit recommended for blow-pipe work.

Dry reagents, such as litharge, borax (crystallized), silica, cyanide of potassium, yellow prussiate of potash, argol, charcoal, starch, metallic iron, pure lead, nitre, powdered lime, sulphur, carbonate of ammonia and common salt are necessary. As solvents and precipitants, distilled water, sulphuric, nitric and hydrochloric acids, chloride of sodium, nitrate of silver and sulphuretted hydrogen are also indispensable.

This will seem rather a formidable list, and so, under certain conditions, it may be; indeed, where means of transport is limited, all regular assay work must be postponed until the return to civilization. Assaying is not, however, difficult, being mostly a matter of rule of thumb, and correct results may be arrived at without a deep knowledge of chemistry, although such knowledge will never come amiss.

A preliminary examination will show what the ore probably is. The blow-pipe is especially useful, though to the skilled assayer often unnecessary. The ore is first powdered, and any metallic flakes picked out and tested separately. A fair sample must be selected, otherwise all the work will be thrown away and the result be valueless.

The next step is weighing the ore and the reagents. Moisture is drawn off by heating in a crucible, a low heat being sufficient. Roasting will eliminate sulphur, antimony, arsenic, etc., and must take place in a flat dish, so that the air may have free access. The powder should be stirred frequently.

Reduction is the operation of removing oxygen, and it takes place usually in a crucible or scorifier.

Scorification consists in placing the ore in an open dish with proper reagents, and collecting all the volatile ingredients in the slag. Cupellation, on the other hand, collects them in the bone ash, of which the cupel is composed.

When silver must be separated from gold, it is sometimes convenient to increase its proportion by the addition of some known weight of the inferior metal. After fusing, the globule is placed in nitric acid, and the silver parted from the gold, which may then be weighed. This result subtracted from the weight of the original globule gives the amount of silver.

To test an ore for gold, take a pound of it, crush in mortar and pass through a fine sieve. Take one-fourth ounce Troy of the powder. Place in scorifier with an equal amount of litharge. Cover with borax that has been melted and powdered, and put the scorifier in the muffle of the furnace. A blacksmith's forge might do at a pinch. Heat until the mass has become a fluid, possibly twenty or thirty minutes. Next pour into the scorification mould, and, after the slag has set, remove it with a hammer. Hammer the button into a cube and place it in the cupel, which must first have been thoroughly heated. Heat until all the base metal has been absorbed by the cupel and the button has "brightened," or flashed; when this occurs, remove the cupel to the front of the muffle, cool, and remove the button with pincers. Weigh it, and you have the amount of gold and silver in ¼-ounce Troy. A simple sum in proportion gives the amount in a ton.

All ores containing sulphur, arsenic, antimony, or zinc, should be roasted.

There are three stages in the scorification process; roasting, fusion, and scorification. During the first, the heat should be moderate until fumes cease to be given off; during the second, the heat is raised and a play of colors is seen on the surface of the lead; in the closing stage, the heat is lowered for a time until the slag covers the lead, when it is again raised for a short time and the scorifier removed. Brittle buttons may be due to arsenic, antimony, zinc or litharge, and must be re-scorified before cupellation, with more lead.

Take the cupel slowly from the fire to avoid "spitting," by which portions of the buttons are lost. Watch closely for the brightening.

Silver is volatile at a high heat, but when the muffle is almost white, the metal well fused and clean, the fumes rising slowly, and the cupel a cherry red, all is going smoothly. If the fumes rise rapidly, the muffle is too hot. On the other hand, dense, falling fumes show the temperature is too low. Lead that is poor in silver stands the highest heat without vitiating the assay.

When the material in the cupel "freezes," i.e., the absorption by the cupel stops, reject the assay and try again, giving more heat or more lead.

Gold. Practically, the metal most prospectors seek is gold. It is so enormously valuable and constitutes so very small a percentage of any ore, that care must be taken or it may escape detection and be lost. Panning is the miner's method. He crushes his ore thoroughly, and places it in the pan with water; then, with a motion easy to learn but difficult to describe, he swirls the water around, allowing a little of it to escape at each revolution, carrying with it the rubbish, until finally he has a little black sand and perhaps a few grains of yellow substance, which is gold. Mica, or fool's gold, puzzles nobody but the ignoramus. True, it looks like gold in certain positions and lights, but gold will beat out thin under the hammer, just as lead would, while mica will break up into a floury powder. Mica is very light, while gold is very heavy; so there is no excuse for confounding the two. If an ore contains sulphurets and gold, the latter may be coated with some sulphur or arsenic, which would prevent the gold from amalgamating. The only remedy for this is roasting. No single acid will dissolve gold, but a solution known as aqua regia, made up of three parts of hydrochloric acid and one part of nitric acid, dissolves it. If to the solution so obtained you add some sulphate of iron, you will get a precipitate which is metallic gold, although it does not look like it, as it is brown in color; but if you place this precipitate in a crucible and heat, you will get a yellow bead of pure gold. Another test for gold is to take the solution as above obtained and add thereto a solution of chloride of tin, when you obtain a purple coloration that has been called the purple of Cassius.

Gold may be distinguished from all other metals by the three following tests: It is yellow; it may be flattened by the hammer; it is not acted upon by nitric acid.

Pure gold is soft, and the point of a knife will scratch it deeply. Pounded in a mortar, the pulverized mineral should be passed through a cheese-cloth screen stretched over a loop of wood. If the course contains much pyrite, it must be roasted before washing in the pan and amalgamating. Sample well, weigh out two pounds, put it in a black iron pan, with four ounces of mercury, four ounces of salt, four ounces of soda and a half gallon of boiling water. Stir with a green stick, and agitate until the mercury has been able to reach all the gold. Pan off into another dish so as to lose no mercury, squeeze the amalgam through chamois leather or new calico previously wetted. The pill of hard amalgam may be placed on a shovel over the fire or in a clay tobacco pipe and retorted.

Gold is readily acted upon by the mixture of nitric and hydrochloric acids known as aqua regia, or by any solution producing chlorine. Some of the mixtures which attack it are bisulphate of soda, nitrate of soda and common salt, hydrochloric acid and potassium chlorate, and bleaching powder. The action is more rapid in hot than in cold solutions, and impure gold is more easily dissolved than pure.

Mercury dissolves gold rapidly at ordinary temperatures, the amalgam being solid, pasty or liquid. Gold rubbed with mercury is immediately penetrated by it. An amalgam containing 90 per cent. of mercury is liquid; 87.5 per cent., pasty; 85 per cent., crystalline. These amalgams heated gradually to a bright red heat lose all their mercury, and hardly any gold. About one-tenth of 1 per cent. of mercury remains in the gold until it is refined by melting.

The veins from which the gold of the world is won do not, on an average, hold the precious metal in greater proportion than one part of gold in 70,000 parts of veinstone. Under favorable conditions a proportion not one-fifth as rich as this, may yield a rich return. In hydraulic mining on a large scale, one part of gold in 15,000,000 parts of gravel has paid a dividend.

A test known as Darton's is believed to be a valuable means of detecting minute quantities of gold in rocks, ore tailings, etc.

"Small parts are chipped from all the sides of a mass of rock, amounting in all to about ¼ ounce. This is powdered in a steel mortar and well mixed. About half is placed in a capacious test tube, and then the tube is partly filled with a solution made by dissolving 20 gr. of iodine and 30 gr. of iodide of potassium, in about 1½ ounces water. The mixture thus formed is shaken and warmed. After all particles have subsided, dip a piece of fine white filter paper in it; allow it to remain for a moment; then let it drain, and dry it over the spirit lamp. It is next placed upon a piece of platinum foil held in a pincers, and heated to redness over the flame. The paper is speedily consumed; and after again heating to burn off all carbon, it is allowed to cool and is then examined. If at all purple, gold is present in the ore, and the relative amount may be approximately deduced. This method takes little time, and is trustworthy."

Black sand, which is iron, often with some platinum and iridium, sometimes interferes with the result of a gold assay. Attwood recommends the following method as applicable to such a case:

"Take 100 to 1000 grains and attack with aqua regia in a flask; cool for about thirty minutes or more; dilute with water and filter. If gold is present, it will now be held in solution in the filtrate. Remove the filter and evaporate the filtrates to dryness; then add a little hydrochloric acid, evaporate and re-dissolve the dry salt in warm water; add to the solution so formed proto-sulphate of iron; which will throw down the gold in the form of a fine, dark precipitate. The precipitate is seldom fine, being mixed with oxides of iron, and must now be dried in the filter paper, and both burned over the lamp in a porcelain dish. Then mix the dried precipitate with three times its weight of lead; fuse, scorify and cupel. In case platinum, iridium, etc., are found associated with the gold, an extra amount of fine silver should be added before cupellation, and the gold button will be found pure."

In one of his reports the State Mineralogist of California gives a most lucid description of a mechanical assay of gold-bearing sands, stamped ore, etc., etc. He states:

"It must be understood that this is only a working test. It does not give all the gold in the rock, as shown by a careful fire assay, but what is of equal importance to the mine-owner, mill-man, and practical miner, it gives what he can reasonably expect to save in a good quartz mill. It is really milling on a small scale. It is generally very correct and reliable, if a quantity of material be sampled. The only operation which requires much skill is the washing, generally well understood by those who are most likely to avail themselves of the instructions. These rules apply equally to placer gravels. Take a quantity of the ore—the larger the better—and break it into egg-sized pieces. Spread on a good floor, and with a shovel mix very thoroughly; then shovel into three piles, placing one shovelful upon each in succession until all is disposed of. Two of the piles may then be put into bags. The remaining pile is spread on the floor, mixed as before, and shovelled in the same manner into three piles. This is repeated according to the quantity sampled, until the last pile does not contain more than 30 pounds of ore. As the quantity on the floor becomes smaller, the lumps must be broken finer until at last they should not exceed one inch in diameter. The remainder is reduced by a hammer and iron ring to the size of peas. The whole 30 pounds is then spread out, and after careful mixing portions are lifted with a flat knife, taking up the fine dust with the larger fragments, until about 10 pounds have been gathered. This quantity is then ground down fine with the muller, and passed through a 40-mesh sieve. If the rock is rich, the last portion will be found to contain some free gold in flattened discs, which will not pass this sieve. These must be placed with the pulverized ore, and the whole thoroughly mixed, if the quantity is small, but if large must be treated separately, and the amount of gold allotted to the whole 10 pounds and noted when the final calculation is made.

"From the thoroughly-mixed sample, two kilogrammes (2000 grammes) must be carefully laid out. This is placed in a pan or, better, in a batea, and carefully washed down until the gold begins to appear. Clean water is then used, and, when the pan and the small residue are cleaned, most of the water is poured off and a globule of pure mercury (which must be free from gold) is dropped in, a piece of cyanide of potassium being added with it. As the cyanide dissolves, a rotary motion is given the dish, best done by holding the arms stiff and moving the body. As the mercury rolls over and ploughs through the sand, under the influence of the cyanide it will collect together all the particles of free gold. When it is certain that all is collected, the mercury may be carefully transferred to a small porcelain cup or test tube, and boiled with strong nitric acid, which must be pure. When the mercury is all dissolved the acid is poured off, more nitric acid applied cold, and rejected, and the gold is then washed with distilled water and dried.

"The object of washing with acid the second time is to remove any nitrate of mercury which might remain with the gold, and which is immediately precipitated if water is first used.

"The resulting gold is not pure, but has the composition of the natural alloy. Before accurate calculations of value are possible, the gold must be obtained pure and weighed carefully. To purify the gold it should be melted with silver, rolled out or hammered thin, boiled twice with nitric acid, washed, dried, and heated to redness.

"The method of calculating this assay is simple. It will be observed that 2000 grammes represent a ton of 2000 pounds; then each gramme will be the equivalent of one pound avoirdupois, or one 2000th part of the whole, and the decimals of a gramme to the decimals of a pound. Suppose the ore yielded by the assay just described, fine gold weighing .072 gramme, it must be quite evident that a ton of the ore would yield the same decimal of one pound. Now one pound of gold is worth $301.46, and it is only necessary to multiply this value by the weight of gold obtained in grammes and decimals to find the value of the gold in a ton of ore—$301.46 × .072—$21.70. The cyanide solution should be kept rather weak, as gold is slightly soluble in strong solutions of cyanide of potassium. Cyanide is a deadly poison."

Touchstones are useful in deciding the probable value of gold alloys. Several pieces of the metal under examination are cut with a cold chisel, and the fresh edges drawn over the touchstone. These streaks are touched with nitric acid on a glass rod. Should no reaction follow, the gold is at least 640 fine. Wipe the stone with soft linen and try with test acid, made by mixing 98 parts of chemically pure nitric acid with two parts of hydrochloric acid, adding 25 parts distilled water by measure. If this has no effect, take a touch needle marked 700, and make a similar streak on the stone samples. Compare, and, if necessary, continue with the other needles, using a higher number each time. An approximate estimate of the sample will soon be obtained. Should the gold seem poorer than 640 fine, try with the copper or silver needle. Practice and a good eye soon make this method very certain in its results.

Retorted amalgam is likely to contain mercury. To test for it, put a small fragment into a closed glass tube, taking care that it falls quite to the bottom. Heat the gold over a spirit lamp, and a deposit of mercury will soon be seen upon the colder sides of the tube above the bottom. The tube may be broken and the mercury collected into a globule under water.

In mining regions gold dust passes current as coin, according to what is supposed to be its value. Occasionally counterfeit dust is offered. The readiest means by which it may be detected are as follows: The dust from any one district is always much alike, and any unusual appearance should create suspicion. Try any doubtful pieces on a small anvil, remembering that gold is extremely malleable. Test some of the gold with nitric acid; effervescence or evolution of red fumes, or coloration of the acid prove impurities to be present. Place two watch-glasses (most useful in chemical tests) on paper; the one on a white sheet, the other on a black, and with a glass rod convey a few drops of nitric acid from the dish to each. To the glass on white paper add a drop or two of ammonia; a blue color would indicate copper. To the other add hydrochloric acid; should a white precipitate form, it proves silver. If no action is noticed, even after heating the dish, the dust is genuine. As "dust" is sometimes merely copper coated with gold, the better plan is to cut all the larger grains in two, so that the acid may attack the copper should it be present.

Copper. Copper is a very easy mineral to test for. First crush the ore and dissolve it in nitric acid by heating. Then dilute with some water, and add ammonia. The solution should turn dark blue. The carbonate ores of copper do not extend deep in the mine. Their places are taken by copper pyrites. Sulphide ores are usually difficult to treat, and when they are to be tested it is better to roast them before trying the tests for color.

Test for copper may also be made as follows:

The sample must be pulverized. Take an ounce of the powder, and place in a porcelain cup. Add forty drops of nitric acid, twenty drops of sulphuric acid and twelve drops of hydrochloric acid. Boil over the spirit lamp until white fumes arise. When cool, mix with a little water. Filter and add a nail or two to the liquid. The copper will be precipitated, and may be gathered up and weighed. The amount of copper in the sample multiplied by 32,000 will be the copper in a ton of the ore.

Should copper be suspected, roast the powdered ore and mix with an equal quantity of salt and candle grease or other fat; then cast into the fire, and the characteristic flame of copper—first blue and then green—will appear. This test is better made at night.

Coal. Coal is often more valuable than gold, and the prospector should be prepared to estimate the value of any seams he may come across during his travels. The following is a very rough but wonderfully effective test for coal. Take a clay pipe, pulverize your sample, weigh off twenty pennyweights, and place it in the bowl of the pipe. Make a cover with some damp clay. Dry thoroughly, and put the bowl upside down over a flame. The gas in the coal will come out through the stem, and may be lit with a match. Let the pipe cool after the gas has all escaped, break off the covering of clay, and if the coal was adapted for coke the result will be a lump of that substance in the bowl. Weigh this. The difference in weight between the coke and the twenty pennyweights of coal that were placed in the bowl will represent the combustible matter forced out by the heat. Now take this coke and burn it on a porcelain dish over the lamp. You will have more or less ash left, and the difference in weight of the ash and the coke will be the amount of fixed carbon in the coal. Your test is complete, and it need not have cost you even the pipe. Sulphur is a detriment to coal, and if you notice much of it in the escaping fumes, you may be sure your sample is not worth much.

Mercury. Cinnabar, the common ore of mercury, is a sulphide. Scratch it with a knife, and the streak will be bright crimson. Dissolve the ore in nitric acid, add a solution of caustic potash, and you have a yellow precipitate. A very pretty test is to place the ore pulverized in a glass tube with some chloride of lime; close the top of the tube, and place a smaller one therein, so bent that it will pass into a basin of water; heat the bottom of the tube containing the ore and lime, keeping the upper part and the small tube cold with wet rags, and you will have a deposit of quicksilver in the basin.

Silver. Silver ore may be detected by dissolving a small quantity in a test tube with a few drops of nitric acid. Boil until all the red fumes disappear. Let the solution cool, and add a little water. Filter the whole, and add a few drops of muriatic acid, which will precipitate the white chloride of silver. Dissolve this precipitate with ammonia; then add nitric acid once more. Exposed to the light, the precipitate soon shows a violet tint. Pure silver is the brightest of metals, of a brilliant white hue, with rich luster. To detect chloride of silver in a pulp, rub harshly with a clean, bright and wet copper cartridge or coin, and if there be silver in the pulp the copper will be coated with it. Graphite will also whiten copper, but the film is easily rubbed off.

Nickel. Nickel may be determined as follows: A little of the powdered ore taken up on the point of a penknife, and dissolved in a mixture of ten drops of nitric and five drops of muriatic acid, should be boiled over a lamp for a few minutes, and ten or twelve drops of water added. A small quantity of ferrocyanide of potash will throw down a whitish-green precipitate, indicating nickel.

Platinum. Platinum is a most refractory metal to treat, as it must be boiled for at least two hours in the mixture of muriatic and nitric acid, known as aqua regia. A small amount of alcohol is to be added to the solution, and the latter filtered. The platinum is precipitated with ammonia chloride.

Manganese. Manganese may be proved as follows: A few grains of powdered ore are placed in a test-tube, with three or four drops of sulphuric acid. Two or three grains of granulated lead or litharge being dropped in, the color will become pink should manganese be in the ore.

A preliminary examination of a mineral may be made with a pocket lens and a penknife. With the first, any conspicuous constituents may be recognized, while a scratch with the point of the latter will give an idea as to the softness or hardness of the mineral. Should much quartz (silica) be present, a sharp blow with the steel will cause sparks.

The next test should be with some ore powdered and held over a spirit flame. A drop or two of water and a drop of sulpho-cyanide of potash will reveal iron, should such be present, by a deep red coloration.

To another portion add one drop of hydrochloric acid, and a dense, curdy precipitate will indicate silver, if there be any.

Added to the same original nitric acid solution, several drops of ammonia water would detect copper by a blue color.

Antimony, tin, aluminum, zinc, cobalt and nickel, uranium and titanium are best shown by the blowpipe.

Carbonates, that is those minerals that contain carbon and oxygen in addition to the metal, effervesce when brought into contact with hydrochloric acid. Some sandstones have a small amount of lime carbonate, and must be tried under the lens, as the bubbles are microscopic. These tests are extremely useful, but by no means infallible, owing to so few ores being pure.

When the explorer wishes to know all the constituents of the ore he has found, he must analyze it. An analysis gives every substance in the ore. Such examinations may be either by the "dry" or "wet" methods, though usually the term "analysis" is restricted to the latter, and "fire assay" is used to describe the former. The wet assay for silver, lead or mercury is effected as follows:

Drop a little powdered ore in a test tube; add nitric acid; dilute with 1/8 water; warm gently over the spirit lamp. It may dissolve or it may not. In the latter case, add four times as much hydrochloric acid. Should all these attempts fail, a fresh sample must be taken, and equal parts of sodium carbonate and potassium carbonate added, and the whole strongly heated in a platinum crucible. The contents, after cooling, is dissolved in dilute nitric acid.

In any case the assay will now be dissolved, and will be in the solution. Filter. Pour ten drops into a test tube; add three or four drops of hydrochloric acid. A precipitate appears. It may be silver, lead or mercury. If silver, it grows dark violet after exposure to sunlight, or 30 or 40 drops of ammonia dissolves it in a few moments. Should it not dissolve, it is lead or mercury. Test for lead by filtering, and heating some of the precipitate on charcoal before the blow-pipe. A bead and yellow incrustation indicate lead. Should none of these things happen, then the metal is mercury. Filter; place in glass tubes; heat gently, and a mirror of quicksilver will appear on the sides of the glass.

This is as far as the prospector, without the various reagents and chemicals that the analyst has always at hand, will be able to go. More complex treatment must be reserved until a return to civilization.

  CHAPTER III.

BLOW-PIPE TESTS.

As a means of readily detecting the presence of minerals in their ores the blow-pipe, in the hands of a skillful operator, is unrivaled. Nor is this skill at all hard to come by; two or three weeks' patient study under a good master should teach a great deal, and subsequently proficiency would come by practice in the field. Unfortunately, some very clever men have become so enthusiastic as to blow-pipe work that they have devised methods by which the amount of metal in an ore as well as its nature may be determined, but in so doing have so enlarged the amount of apparatus, and complicated the tests so seriously that the simplicity of the blow-pipe outfit is in danger of being lost, and its chief advantage of being forgotten; for there are many better ways of determining the value of an ore. A good assay or, better still, a mill run, is worth incomparably more than any quantitative blow-pipe test, even when conducted by a Plattner.

The chemical blow-pipe is made of brass or German silver, with platinum tip.

The best fuel, taking everything into consideration, is a paraffin candle in cold climates, and a stearine candle in hot ones. Tallow may do in an emergency, but it requires too much snuffing.

The blow-pipe can produce two flames. The one known as the reducing flame, and generally printed as R.F.; and the oxidizing flame, represented by the initials O.F. In the first the substance under examination is heated out of contact with the air and parts with its oxygen. In the second, it is heated in the air and absorbs oxygen.

Well-burnt pine or willow charcoal in slabs 3 inches by 1¾ inches is the material upon which the mineral to be tested is placed. A small shallow depression is scraped out of one side of it and the assay placed therein.

Platinum wire, some 3 inches long, conveniently fused into a piece of glass tube as a handle, is used to test the coloration of minerals in the flame. This should be cleaned occasionally in dilute sulphuric acid and then washed in water.

A small pair of forceps with platinum points serve a great variety of purposes, but the beginner must be careful not to heat metallic substances in them to a red heat, as he may thereby cause an alloy of the metal with the platinum and spoil them for future use.

Glass tubing one-twelfth to one-quarter inch in diameter and from four to six inches in length is used for a variety of purposes. From this material what are known as closed tubes may be made by heating a piece of the tubing at or about its center over a spirit lamp, and, when the glass has fused, pulling it apart. These closed tubes are used in heating substances out of contact with the air.

A small agate mortar is indispensable. It must be used for grinding substances softer than itself to a powder, but it will break if rapped sharply.

A small jeweler's hammer is used to flatten metallic globules upon any hard surface A regular blow-pipe outfit would include a small anvil for this purpose, but it is hardly necessary, as any iron or steel surface will do.

A magnet will detect the presence of any magnetic mineral, especially if it is reduced to powder and the test made under water.

Two small files, one three-cornered and the other rat-tailed, must be included in the list of requisites. By means of the former, glass tubing may be notched and pulled or pushed apart, and the latter is necessary in fitting glass tubing to the cork of wash-bottles and other apparatus.

A good lens is indispensable. That known as the Coddington is as good as any.

A dozen test tubes of hard glass, with stand, in small and medium sizes, should not be forgotten.

A glass funnel 2½ inches in diameter is requisite in filtering. The circular filter papers are folded in four and placed in the funnel, point down, three thicknesses of the paper being on one side of the funnel and one thickness on the other.

A wash-bottle is made from a flask into which a sound cork has been placed with holes in it for two pieces of glass tubing. The one serves as a mouth-piece into which the operator blows, while the other, reaching almost to the bottom of the bottle and ending in a spout outside the cork, permits a stream of water to be forced out of the bottle when it is blown into.

A few glass rods in short lengths do for stirrers. A little ingenuity is better than much apparatus.

Of reagents, all those to be found in a well-appointed laboratory may occasionally be of service, but the rough and ready prospector can get along fairly well with the following: Carbonate of soda, borax, microcosmic salt, cobalt solution, cyanide of potassium, lead granulated, bone ash, test papers of blue litmus and turmeric, the former for proving the presence of acid in a solution and the latter that of an alkali.

The foregoing are all dry reagents. Among the wet reagents are: Water—clean rainwater—or, better still, distilled water; hydrochloric acid, sulphuric acid, nitric acid, ammonia, nitrate of cobalt.

Heating a mineral with carbonate of soda on charcoal is accomplished as follows: The pulverized mineral, intimately mixed with three times its bulk of carbonate of soda, is placed in the cavity on the coal. Tin ore, which is very difficult to reduce, should have a fragment of cyanide of potassium placed upon it after it has been heated for a few seconds, and the flame is then reapplied. A globule of metal should result, and perhaps an incrustation on the coal. The reaction is as follows:

A small loop is made at the end of the platinum wire, and it is heated and dipped in borax; heated again, then touched while hot to the powdered mineral and heated once more. The following colors are obtained:

COLOR OF BEAD.

The substance to be tested is generally powdered and moistened, placed in the cavity and covered or not as circumstances may demand, with a pinch of carbonate of soda or other suitable reagent. The following results may be obtained:

Antimony. Place the mineral in the cavity with a little of carbonate of soda, and blow upon it with the inner or oxidizing flame. This is formed by inserting the blow-pipe an eighth of an inch into the flame and blowing steadily. A white incrustation on the coal, and a brittle button of antimony should be the result.

Lead. Treat the suspected lead ore the same way, and you will get a yellow incrustation on the coal and a button of malleable lead.

Zinc. Proceed as above, and after blowing for a few seconds moisten the incrustation with a drop of nitrate of cobalt. Heat once more, but this time use the outer or reducing flame, which is produced by keeping the point of the blow-pipe a little outside the flame and blowing more gently than before, so that the whole flame playing upon the coal may be yellow in color. A green incrustation will be an evidence of zinc.

Copper. As usual, mix the ore and the soda into a paste and fuse it with the oxidizing flame. Dig the mass out of the charcoal with the point of a knife and rub it in the mortar with water. Now decant into a test tube, and, allowing the sediment to settle, pour off the water. If there was copper in the ore, red scales will be found in the test tube.

Arsenic. Heat in the inner flame for a second or two, and if the ore contains arsenic you will notice an odor of garlic.

Tin. This is a very difficult ore to reduce, but the addition of a little cyanide of potash to the powdered ore will make it easier. Fuse, after moistening on the charcoal, in the oxidizing flame, and you will probably obtain small globules of tin.

Silver. Make a paste of the ore with carbonate of soda; add a small piece of lead and fuse into a button. Make a second paste of bone ash and water, and after you have dried it with a gentle flame place the button of silver and lead on the bone ash, and turn on the oxidizing flame. The lead will disappear, leaving a silver globule. Should it not be pure white, but more or less tinged with yellow, it probably contains gold; and if the button be dissolved in nitric acid, whatever remains behind is gold.

Sometimes it is desirable to determine whether tellurium is present in an ore. This is very easy to find out. All that is required is a blow-pipe, alcohol lamp and a porcelain dish. Break off a small piece of the ore, place it in the dish previously warmed, blow upon the ore with the blow-pipe until it is oxidized, then drop a little sulphuric acid on the ore and dish. If tellurium be present, carmine and purple colors on the assay will proclaim the fact.

Bismuth ores are very heavy; usually they have more or less antimony associated with them, which is a drawback, as the separation is an expensive matter and the returns are less than they would be from a low grade pure ore. In testing for this metal, dissolve a crushed sample in nitric acid and then add potash in excess. If the ore is one containing bismuth, you should have a white precipitate; if it contains cobalt, you will get a bluish-green coloration. Bismuth is worth about fifty cents a pound if pure and free from antimony.

Galena is often mistaken for other ores, specular iron ore for instance. If the ore be crushed and heated in nitric acid until dissolved, some water added, and an addition made to the solution of a few drops of ferrocyanide of potassium, a dark blood-red precipitate is thrown down. If the ore were galena, there would be no coloration. The so-called steel galena which carries a little zinc is generally richer in silver than the ordinary cube galena, though the reverse is sometimes the case.

If lead ore be dissolved in nitric acid, the solution diluted, and some hydrochloric acid added, a white precipitate is thrown down. Add ammonia and the precipitate remains unaltered.

The blow-pipe operator has to learn to breathe and blow at the same time; the breathing he does through the nostrils, the blowing is produced by the natural tendency of the cheeks to collapse when distended with air. A skillful operator can blow for many minutes at a time without the slightest fatigue.

To identify cinnabar, the ore from which quicksilver is obtained, make a paste of the substance in powder and carbonate of soda. Heat in the open tube, and a globule of mercury will result.

Sulphur turns silver black. Make a paste with carbonate of soda, heat on the charcoal, and removing the mass with the point of a knife lay it on a silver coin and moisten. A black sulphide of silver should show quickly on the coin if sulphur is present. Magnesia gives a faint pink color when heated and treated with nitrate of cobalt on coal. Alumina under the same circumstances give a blue color.

Roasting is an oxidizing process, the substance being heated in air, so that it may absorb oxygen.

The test by reduction with soda on coal in the R.F. is particularly valuable in the case of copper ore, as little as 1 per cent. being detected.

  CHAPTER IV.

ECONOMIC ORES AND MINERALS.

Aluminum is derived from two ores, cryolite and bauxite. This metal has made rapid strides into favor during the past half-dozen years. Although known since 1827, it remained a rare substance in the metallic form, though it is the most abundant of any of the metals in its ore. In ordinary clay there is an inexhaustible source of aluminum. But the ores that yield the metal cheaply are few. Until recently, cryolite, found abundantly in Greenland, was the chief source of the metal, but now bauxite is used in its place. Bauxite is a limonite iron ore in which a part of the iron has been replaced by aluminum. It is found in Alabama, Georgia and Arkansas, as well as in Europe. Aluminum is white, and very light in weight. It does not tarnish easily.

The chemical composition of these ores is:

In 1895 the production of this metal in the United States was 900,000 pounds. In 1899 it rose to 6,500,000 pounds. The only firm producing aluminum is the Pittsburg Manufacturing Company of Buffalo, N.Y., who reduce the metal from bauxite, which they obtain in the southern states. One of the latest uses for this metal is for gold miners' pans. The French seem to keep ahead of the rest of the world in finding new uses for aluminum.

Most of the supply of cryolite comes from Greenland, where it occurs in veins running through gneiss rocks. Glass-makers use it and pay good prices for it. Lately makers of aluminum also buy it, as it contains 13 per cent. of that metal.

A new aluminum-bearing mineral, discovered in New Mexico and in Ohio, is called native alum. It gives 50.16 per cent. alumina, and may be treated by solution in warm water, filtration, evaporation and roasting. No estimate has yet been made of the amount available.

As bauxite promises to be in greater demand in the future than in the present, owing to the ever-increasing demand for aluminum, the prospector will do well to make himself thoroughly familiar with its appearance. It is creamy white when free from iron, and the grains are like little peas, or pisolitic. It contains water, aluminum, silica, and generally iron. The French beds near the town of Baux are 30 miles long and 40 feet thick. In the United States, beds have been found in Alabama, Georgia and Arkansas. The Georgia beds are turning out three-fifths of the bauxite produced in America. The ore is in beds and pockets, and enough has been prospected to assure a supply for some years to come, unless the demand should grow very decidedly, in which case a scarcity might soon be felt. The American ore is easier to work than the French, and manufacturers prefer it to any they can import, even though the cost is higher and the percentage of aluminum smaller. The Arkansas deposits are as thick as the French, and only 300 feet above the level of the tide. Imported bauxite cost $5 to $7 a ton in New York City. American ore costs $5 to $12 a long ton. Best selected Georgia brings $10.

Should the deposits of bauxite give out, the manufacturers of aluminum would probably fall back on cryolite. At Tvigtuk, on the west coast of Greenland, it exists, as a very heavy vein, in gneiss. It is semitransparent, and snow-white. Impurities may stain it yellow or red or even black. Its specific gravity is 2.95, and its hardness 2.5 to 3. It is fusible in the flame of a candle, and yields hydrofluoric acid if treated with sulphuric acid. It is still used for making soda and aluminum salts, and an imitation porcelain. It is also in general use as a flux.

Amber. This is a fossil resin, or gum, and may often be found in lignite beds. Recent discoveries have been made on the coast of British Columbia that are expected to supply the world. All pipe-smokers know it.

Antimony. The commercial ore of this metal is the sulphide known as stibnite, or gray antimony. Its composition when pure is 72 per cent. antimony and 28 per cent. sulphur. Hardness is 2; gravity, 4.5; luster, metallic; opaque; gray; cleavage, perfect. Fracture, conchoidal. Texture, granular to massive. The ore tarnishes quickly, is easily melted, or dissolved in hydrochloric acid. The associated minerals are generally the ores of lead, zinc, and carbonate of iron. Baryta may be the gangue or veinstone. Antimony is worth from 10 to 15 cents a pound.

Although antimony occurs in many minerals, the only commercial source is the sulphide, stibnite. Antimony is used as an alloy in type metal, pewter, and babbitt metals. It is injurious to copper, even one-tenth of one per cent. reducing the value of that metal very considerably. The price varies greatly, being now about 10 cents a pound.

The composition of stibnite is:

The production of antimony in this country is not very large. The output of 1899 was but 1,250 tons, valued at $241,250. The ore is worth from $40 to $50 a ton delivered at Staten Island, N.Y.

Apatite suffered in demand when the cheap phosphates of South Carolina were discovered, and these in turn are being ousted from the markets of the world by Thomas slag, an artificial phosphate, and by the easily-mined natural phosphates of Algeria. The price varies with the quality of the rock, from $1.75 to $11 per ton, averaging in 1899, $3.86.

Apatite is a phosphate of lime, containing 43 per cent. of phosphoric acid. It occurs in the old crystalline and primary rocks of Canada, but although still of some value it has yielded the position it once occupied to the Carolina phosphate deposits, which, although not so rich in acid, are softer, and less expensive to utilize. Apatite is doubtless derived from the remains of animals or fishes that lived in the distant past. The colors are often beautiful—green, pink, gray, etc.—but the sheen is always white. Hardness of 4.8. Specific gravity, 3.1.

Asbestos. This fibrous silicate of magnesia and lime is to be looked for among primary rocks near serpentine dike. The fibers of this material may be woven into cloth that will be fire-proof. It is of considerable, though fluctuating, value.

The demand for this material is likely to increase, though at present the supply is fully equal to demand. It is being used in Germany to make fire-proof paper, and in Quebec to make asbestos plaster for covering wood-work. It is generally quarried in open pits, the rock being crushed in a rock-breaker, and the fiber freed from adhering particles of rock and dust. It is then sorted, the longest fibers going into the first quality heap. The production in 1899 in the United States was 912 tons, value $13,860; in Canada, 23,266 tons, value $598,736.

Borax. This mineral is borate of soda. Its composition is: 37 per cent. boric acid, 16 per cent. soda, and 47 per cent. water. Its gravity is 1.7. Hardness, 2.3. It is white, and has a sweetish taste. Borax is valuable, but occurring as it does as an incrustation upon the ground over large areas, a detailed description would be superfluous, as the explorer will surely recognize it should he find it.

Clay. A good bed of clay may be of value in an accessible region. Brick-clay contains silica, alumina, iron, etc. Potters' clay is made by suspending ordinary brick-clay in water, and running off the water and fine particles suspended therein. These are allowed to settle, and, when dry, are fine potters' clay. The better the clay, the larger the percentage of potters' clay. Fire-clay should contain 60 per cent. of silica, and 30 per cent. of alumina. Mixed with sand and burnt into bricks, it will resist great heat. Light-colored clays are preferable for this purpose, as iron is prejudicial to a good fire-brick. Kaolin is the finest porcelain clay, and the best comes from China, Japan or France. It is a product of decay in feldspar rocks. The potash is washed out, and the silica and alumina left as parts of a white clay of fine grain.

Coal. Anthracite is bituminous coal that has been subjected to great heat and pressure; in plain language, baked. It contains over 90 per cent. of carbon. Specific gravity 1.5 to 1.8. Hardness, 2.3 to 2.6. The ash left after burning is white or red. There is little or no sulphur in anthracite. It does not coke.

There are three main divisions of coal, arranged according to their carbon, water and ash. They are:

Good bituminous coal contains about 85 per cent. of carbon, but the composition varies greatly. Cannel coal is a variety of bituminous that gives off much gas. It burns with a bright flame in an open grate, igniting as easily as a candle. Lignite is intermediate between coal and peat. All the Rocky Mountain coals are lignites. It is a very inferior coal at its worst, while at its best it is nearly the equal of a poor bituminous coal.

Some coals will coke and others will not; nothing but a trial can settle this matter in each individual case. Good coking coal is very valuable.

Cobalt. Cobalt ores are always found in veins with other metals. Pure cobalt is extremely rare. Cobalt colors are used for porcelain painting, glass-staining, etc.

Chromium. All chrome is obtained from chromite, which contains 68 per cent. of chrome sesqui-oxide, the remainder being iron protoxide. Hardness, 5.5; gravity, 4.4; luster, sub-metallic; opaque. Steel-gray to almost black. Harsh. Brittle. Cleavage, imperfect. Fracture, uneven. Texture, massive to granular. Chromite in gravel looks like shot. Serpentine often contains it, when it is apt to resemble a fine-grained magnetite. It is used chiefly in iron and steel alloys, and in making armor plate. It is also used in dyeing fabrics and in paint manufacture. But little chrome ore is produced in the United States. The importation in 1899 was 15,793 tons, value $18.03 per ton.

This ore is merchantable at $22 to $25 per ton.

Domestic ore ranges from $10 to $12 a ton, while the pure imported ores are worth $21 a ton. The yearly consumption in the United States is about 16,000 tons, and the American production 100 tons. This ore is useful as a lining for furnaces, and the demand promises to become important. Newfoundland is said to contain large deposits.

Copper. Native copper occurs in the Lake Superior region, but the demands of commerce are supplied from chalcopyrite or copper pyrites, and tetrahedrite or gray copper ore. Many different ores of copper may exist in the same vein. On the surface an iron cap of gossan reveals the deposit; immediately below may be black oxide of copper with some malachite, lower down red oxide, and below the water-line copper sulphides. The following are the principal copper ores:

The common ore is native copper, often associated with native silver, the two remaining, chemically, quite distinct. Some masses of copper occur that are too large to handle and must be cut by cold chisels, a method that costs more for labor than the value of the metal. The Lake Superior mines produce 140,000,000 pounds of copper a year, while those of Montana made the gigantic output of 228,000,000 pounds in 1896. The great Anaconda mine, of Butte, is the heaviest producer, yielding more than half the state's total.

During 1899 the New York copper market rate varied between 14.75 cents and 18.46 cents per pound. Copper is probably abundant in the shape of pyrites in many parts of Canada, especially in the Northwest, and prospectors in that region should search diligently for it. The Lake Superior mines are unique in being deposits of native copper.

Owing to the great demand for copper following upon the extraordinary spread of electricity, copper properties have become so enormously valuable that, possibly, the explorer will be quite as fortunate in finding copper as in finding gold. Moreover, with the exception of Spain and Chili, the United States has no serious rivals in copper production,—Montana and Michigan, producing the greater part of the output. The famous Calumet and Hecla mine, in Michigan, is now down 4,000 feet and still yields ore. The most copper ores are not difficult to distinguish. Every one is familiar with the ruddy hue of pure copper, the color of the native metal. It may be flattened under the hammer or cut with the knife. A little of the ore mixed with grease colors a flame green. Copper ores are heavy, and generally of a bright color, either red, blue, green, yellow or brown.

Corundum. Nine hundred and seventy tons of this abrasive were produced in the United States in 1899; value, $78,570. Corundum is found in feldspar veins, and associated with chlorites in serpentine rock. North Carolina furnishes half the corundum marketed. The presence of this substance is always indicated in the South by serpentine, chrysolite, or olivine rocks; experience being the only guide the miners have in finding new deposits. The contacts of the olivine rocks with gneiss usually produce rich deposits. Corundum is the hardest substance known, next to the diamond. It is used as a polishing powder. Emery is an impure corundum containing iron. Corundum is composed of 53 per cent. aluminum and 47 per cent. oxygen. Specific gravity is 4. Hardness, 9.

Feldspar. The Maine, Pennsylvania, New York, and Connecticut ores are worth $3 to $6 per long ton (2,240 pounds) at point of production.

Fluorspar. The American market is supplied by ore from Rosiclare, Ill., Marion, Ky., Hardin Co., Ill., and Liumpton Co., Ky., and imported spar. It is worth $6 a ton of 2,000 pounds. This spar is softer than quartz and of most brilliant colors, varying through the yellows, greens, blues and reds, to pure white. The streak is always white. Specific gravity, 3. Hardness, 4. It is worth mining when abundant and accessible.

Gems. Gems are to be looked for in a country of crystalline rock, such as granite, gneiss, dolomite, etc. Topaz and ruby are generally discovered in crystalline limestones, while turquoise is usually found in clay slate. It is not likely that the American prospector will come upon the true oriental ruby; he will more probably find the garnet. The ruby is next to the diamond in hardness and in value, and consists practically of pure alumina. The garnet is but as hard as quartz, and is a silicate of alumina with lime and a little iron. They crystallize in different systems, the more valuable gem belonging to the rhombohedral, and the less valuable to the isometric system.

The turquoise which has lately been found in Arizona is not a crystal. The blue color which distinguishes it is derived from copper. It is a phosphate of alumina with water in composition. In form it is kidney shaped or stalactitic. Lazulite, a far less valuable substance, is also blue, but as it crystallizes in the monoclinic system it should not be mistaken for turquoise. Moreover, lazulite is softer and contains magnesia and lime, which the turquoise does not. Lapis lazuli, which is also occasionally mistaken for turquoise, belongs to the regular or isometric system; it is commonly massive or compact, and is a silicate of alumina with some lime and iron. It is found in syenite, crystalline, limestone, and often associated with pyrites and mica.

Topaz belongs to the orthorhombic system. It is a silicate of alumina with fluorine. Powdered, mixed, and heated with microcosmic salt in the open tube, fluorine is disengaged with its characteristic odor, and etching action upon glass. With the blow pipe on charcoal, heated with the cobalt solution, it gives the fine blue color of alumina.

The explorer who comes upon any hard, brightly colored stone, that may possibly turn out a gem, should preserve it carefully until he returns to some city, when it should be submitted to an expert. The value of a gem depends upon so many qualities that it were hopeless for the tyro to endeavor to arrive at any just estimate of it. He might ruin a superb specimen, without becoming one bit the wiser. A few of the more prominent characters of valuable gems follow:

Graphite. This mineral is commonly known as black lead, or plumbago. It is the same in composition as the diamond, viz.: 100 per cent. carbon. Specific gravity, 2 to 2.2. Hardness, 1.2 to 1.9. Color, black. Greasy. Of value when free from impurities. Used in making pencils, stove polish, crucibles, etc. Found in the earlier rocks.

Gypsum. A sulphate of lime occurring in great beds. Burnt, it becomes plaster of paris.

Iron. This, the most important of all metals, is found in various forms. The ores of iron are:

Native iron is only found in meteorites that have come from space.

Magnetite is loadstone ore; the powder is reddish black, and the ore, dark brown to black. It is found in the older rocks and is an important ore.

Hematite varies from metallic to dull in luster. There are many varieties of it, known as ironstone, ocher, needle ore, etc. Hematite may be slightly magnetic. Immense beds exist in the triassic sandstones, and in the secondary rocks below the coal measures. The powder and streak of limonite are always yellow; it is an important ore. Siderite assumes many forms. It is called spathic ore, clay-ironstone, carbonate of iron, black band, etc. Most of these carbonate iron ores only range between 30 and 40 per cent. of metallic iron, but are in demand as fluxes for other iron ores. The pyritic ores of iron, including marcasite, pyrrhotite and mispickel, are often taken for gold by the inexperienced. In an accessible region pyrites may be valuable, as they are bought by makers of sulphuric acid.

Iron is so low in price that vast deposits exist which cannot be made use of because they would be too expensive to mine. A deep bed, or a narrow one, or the slightest difficulty in transportation, would preclude any profitable development. It is known that enormous areas in northern Labrador, for instance, are full of iron deposits, yet there seems no chance of their having the slightest economic value for a long time, if ever. Conditions of commerce very different to those now obtaining will have to exist before they can be utilized.

Iron ore is most favorably situated for profitable extraction when it is near coking coal and beds of limestone; the former for fuel, the latter for flux. Occasionally such regions as that of Lake Superior may be able to compete successfully with others, although they do not possess the necessary smelting facilities, because these deficiencies are counterbalanced by inexhaustive stores of easily mined ores, and transportation facilities unrivaled in cheapness.

Lead. The two important sources of supply are galena and cerussite. The former contains 87 per cent. of lead, and frequently some silver and gold. It is so distinctive as to be easily recognized. Luster, metallic; opaque; lead-gray; harsh. Brittle to sectile (may be cut). Cleavage, perfect. Fracture, even to sub-conchoidal. Structure, granular or foliated, tabular, or fibrous. Specific gravity is 7.5, and hardness, 2.6.

The carbonate cerussite contains about 79 per cent. lead. Luster, vitreous to resinous. Translucent. Color, gray. Smooth. Brittle. Cleavage, perfect to imperfect. Fracture, conchoidal. Massive to granular. Rich carbonate ores look like clay, and are undoubtedly often passed by.

The economic ores of lead are:

Lead ores are frequently rich in silver. They occur in limestone, sandstone, granite and clay. The commercial ores are galena, which is easily recognized by its steel-like cubes, and the carbonates. These latter are like lightly colored clays when in powder and are very apt to be overlooked. Fluor spar is as favorable a gangue for lead as quartz is for gold.

The Rocky Mountains are the principal American sources of this metal, but a very large amount comes from the Mississippi valley. In the mountains the ore is a by-product, in silver smelting, being obtained from argentiferous galena, while in Missouri, Kansas, Wisconsin and Illinois lead and zinc are found free from any mixture with the precious metal. The age of these deposits varies from lower silurian or cambrian to the carboniferous.

The ore is found in limestone rocks,—sometimes in flat openings parallel to the almost horizontal beds, or else in gash veins almost at right angles to these. As lead is often found in dolomite limestone, that is, limestone carrying almost as much magnesia as lime, and this rock was undoubtedly deposited in a shallow sea, geologists incline to the belief that therefore the lead is due to a growth of seaweeds in whose ash this metal and zinc are known to occur. At any rate, these deposits now have great economic value, and the lead and zinc ore is easily got at.

Galena and zinc blende frequently resemble one another, but they may be distinguished by this infallible sign: the powder of galena is black, and that of blende brown, or yellow.

Lithographic Stone. This is a very fine grained compact limestone from Bavaria. So far nothing equal to the imported stone has been found in America. The distinguishing qualities are: Gray, drab or yellow; porous, yet not too soft; of fine texture, and free from veins and inequalities.

Manganese. Manganese ores in 1899 amounted in the United States to 143,256 tons, value $306,476. This mineral is used for bleaching and making oxygen, and in steel manufacture. Pyrolusite contains 63 per cent. manganese. Hardness, 2.3. Specific gravity, 4.8. Luster, metallic. Opaque. Gray to bluish black. Harsh. Brittle. Cleavage, imperfect. Fracture, uneven. Granular, massive. Manganite is harder, 4.0; its specific gravity is 4.3. Luster, sub-metallic. Cleavage, perfect. Texture, fibrous. Wad is an impure ore of manganese found in bogs, of little or no value.

Franklinite, a zinc-manganese ore, is also a common source of supply. An ore to be commercially valuable should contain from 40 to 60 per cent. metallic manganese, and not over 0.2 to 0.25 per cent. phosphorus.

To determine the value of manganese ores a somewhat intricate calculation is necessary. Delivered at Bessemer, Pa., the Carnegie Steel Company pays according to the following sliding scale:

Moreover, for each one per cent. of silica in excess of eight per cent. a deduction of fifteen cents a ton is made, and a deduction of one cent per unit of manganese is made for each 2/100 of one per cent. of phosphorous present in excess of 1/10 per cent. From which it is evident that there can be little profit in impure deposits of manganese.

Mercury. Quicksilver usually occurs in the form of cinnabar, though occasional deposits of pure metal are found in drops and small pockets, in limestone and the softer secondary rocks, including shales and slates. As the appearance of quicksilver must be familiar to all, cinnabar alone needs description. Its specific gravity is 9.0; its hardness, 2.2. It is a red brown earthy ore, the powder of which is a dull red. It is generally found in sandstone, though it occasionally occurs in slates, shales and serpentine. Heated gently with lime cinnabar yields quicksilver. If copper be held over the fumes of mercury it will be coated with a light film of the metal. An alloy with silver has been found. Mercury is heavy, extremely brilliant, and mobile. The composition of cinnabar is: