Arrowheads made from white, gray, pink, and black chert. (Courtesy of Mr. A. A. Jeffrey, Columbia, Mo.)
Sedimentary rocks are those whose particles settled down through the air or water to form rocks in layers or beds; hence layered, bedded, or so-called stratified rocks are sedimentary rocks. For instance, the sand and mud settling out of the Gulf of Mexico (or ocean) after being brought in by the Mississippi River is on its way toward becoming sandstone and shale. Limestone is forming off the coast of Florida now. All of these rocks are accumulating in layers. Where one sees regularly-layered or stratified rocks in streams, road cuts, quarries, bluffs or hillsides, he expects them to be sedimentary rocks. The sedimentary rocks that have been described herein include:
Diaspore and Burley clay
Igneous rocks are those which solidified from a hot liquid which was either forced into older surrounding rocks (intrusive) or discharged on the earth’s surface as a lava flow or products from a volcano (extrusive).
The examples given below illustrate the two types. Everyone knows about the extrusive forms from accounts of present-day volcanoes and occasional lava flows, like those of Vesuvius, Paricutin, and Mauna Loa. An intrusion was injected beneath the Yellowstone Park area years ago, and its heat, with steam and gases, is contributing to the unusual natural features which are found in the park and which make it famous.
Igneous rocks in Missouri are:
Metamorphic rocks are rocks which have been changed through the effects of tremendous pressure (enough to raise mountains) and high temperature while in the solid state. In most cases a banded rock results. The metamorphic rocks mentioned in this booklet are:
No doubt it has become apparent to the reader that rocks ordinarily occur in great quantities, that they are composed of multitudes of grains (mineral grains), and that their properties and compositions vary with the different minerals which are present in the grains of the rock. A rock can, therefore, be different from a mineral. In fact, a rock may be defined as “an aggregate of mineral particles,” or more broadly “a typical part of the earth.” To focus closer attention on minerals we may discuss them for their own sake below.
A mineral is characterized by a constancy of composition and of properties which sets it apart from rocks which vary widely. Minerals may be metallic, like pyrite, or non-metallic, like barite; they may be ore, like galena, or rock-forming, like quartz or feldspar; they may show crystal faces, or they may be fragments with rounded or broken surfaces. A favored definition teaches that “a mineral is a naturally occurring, inorganic substance having a definite chemical composition and definite physical properties, within limits.” The Missouri minerals listed herein include:
Although the emphasis in this pamphlet has been on the recognition of Missouri rocks and minerals, it is not out of order to consider the broad values that they contribute to our civilization. Their use as building materials has been noted, but it should be further recognized that as our timber is being rapidly depleted more and more structures will be built out of earth materials. Missouri possesses a wealth of beautiful limestone that is serviceable and readily quarried. Where limestone is not near, there is usually shale or glacial clay which can be used in the manufacture of brick and tile. Permanency will be the keynote of the rock and ceramic structures. Gravel and sand are abundant in Missouri for concrete and other varied uses.
The soil is Missouri’s most valuable earth material. Hundreds to thousands of years of normal weathering are required to develop the rocks and minerals and texture of the inorganic fraction of the soil. We should preserve it and prevent disastrous soil erosion.
Aside from these more tangible values, a fascinating and instructive hobby can be made of collecting, arranging, and studying rocks and minerals. One gains a fuller understanding and appreciation of nature from their study. The orderliness, constancy, and interrelation within the rock and mineral “world” is a restful contrast to the one which man often keeps in turmoil. The beauty of a glistening crystal or a polished mineral or stone is as inspiring as a lovely flower, yet it lasts and lasts through centuries, a veritable “rock of ages.”
How to Know the Minerals and Rocks, by Pearl; publisher, McGraw-Hill Book Co., New York.
A Field Guide to Rocks and Minerals, by Pough; publisher, Houghton, Mifflin Co., Boston.
Gemstones and Minerals: How and Where To Find Them, by Sinkankas; publisher, Van Nostrand, Princeton, New Jersey.
Look for paper back editions of these and other books which may be widely available.
The Common Fossils of Missouri, by A. G. Unklesbay, Missouri Handbook No. 4.
Rocks and Minerals, Box, 29, Peekskill, N.Y.
Gems and Minerals, P.O. Box 687, Mentone, Calif.
The Mineralogist, P.O. Box 808, Mentone, Calif.
American Mineralogist, technical official publication of the American Mineralogical Society, Ann Arbor, Michigan, editorial office, Dept. of Mineralogy, University of Michigan.
Dana’s Manual of Mineralogy, by Hurlbut; publisher, John Wiley & Sons, New York.
Dana’s Textbook of Mineralogy, by Ford; publisher, John Wiley & Sons, New York.
Mineralogy, by Berry and Mason; publisher, Freeman & Co., San Francisco.
Rocks and Rock Minerals, by Knopf; publisher John Wiley & Sons, New York.
Guide to the Study of Rocks, by Spock; publisher, Harper & Co., New York.
Introduction to Geology, by Branson, Tarr, and Keller; publisher, McGraw-Hill Book Co., New York City.
Introduction to College Geology, by Holmes; publisher, Macmillan, New York.
Geology, by Emmons, Thiel, Stauffer and Allison; publisher McGraw-Hill Book Co., New York.
Principles of Geology, by Gilluly, Woodford, and Waters; publisher, Freeman & Co., San Francisco.
Physical Geology, by Leet and Judson; publisher, Prentice-Hall & Co., New York.
The Geological Evolution of North America, by Clark and Stearn; publisher, Ronald Press Co., New York.
Time, Life, and Man, by Stirton; publisher, John Wiley & Sons, New York.
These books may be borrowed from public libraries, or purchased from the publishers and retail book stores. At Columbia, the University Book Store, and the Missouri Store Co., sell most of them from shelf stock.
Missouri has an excellent State Geological Survey which has published numerous volumes on various geologic topics and areas within the State. Inquiry about these bulletins, circulars, maps, and individually handled correspondence, should be addressed to the:
State Geologist
Missouri Geological Survey
Rolla, Mo.
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