CHAP. 43.—TOUCHSTONES FOR TESTING GOLD.
A description of gold and silver is necessarily accompanied by that of the stone known as “coticula.”1037 In former times, according to Theophrastus, this stone was nowhere to be found, except in the river Tmolus,1038 but at the present day it is found in numerous places. By some persons it is known as the “Heraclian,” and by others as the “Lydian” stone. It is found in pieces of moderate size, and never exceeding four inches in length by two in breadth. The side that has lain facing the sun is superior1039 to that which has lain next to the ground. Persons of experience in these matters, when they have scraped a particle off the ore with this stone, as with a file, can tell in a moment the proportion of gold there is in it, how much silver, or how much copper; and this to a scruple, their accuracy being so marvellous that they are never mistaken.