BOOK VII

INCE the Sixth Book has described the iron tools,the vessels and the machines used in mines, thisBook will describe the methods of assaying 3 ores;because it is desirable to first test them in orderthat the material mined may be advantageouslysmelted, or that the dross may be purged away andthe metal made pure. Although writers have men-tioned such tests, yet none of them have set down thedirections for performing them, wherefore it is nowonder that those who come later have written nothing on the subject.By tests of this kind miners can determine with certainty whetherores contain any metal in them or not; or if it has already beenindicated that the ore contains one or more metals, the tests show whetherit is much or little ; the miners also ascertain by such tests the method bywhich the metal can be separated from that part of the ore devoid of it;and further, by these tests, they determine that part in which there is muchmetal from that part in which there is little. Unless these tests have beencarefully applied before the metals are melted out, the ore cannot be smeltedwithout great loss to the owners, for the parts which do not easily melt in thefire carry the metals off with them or consume them. In the last case, they passoff with the fumes; in the other case they are mixed with the slag and furnaceaccretions, and in such event the owners lose the labour which they have spentin preparing the furnaces and the crucibles, and further, it is necessary for themto incur fresh expenditure for fluxes and other things. Metals, when they havebeen melted out, are usually assayed in order that we may ascertain what pro-portion of silver is in a centumpondium of copper or lead, or what quantity ofgold is in one libra of silver ; and, on the other hand, what proportion of copperor lead is contained in a centumpondium of silver, or what quantity of silver iscontained in one libra of gold. And from this we can calculate whether itwill be worth while to separate the precious metals from the base metals, ornot. Further, a test of this kind shows whether coins are good or aredebased; and readily detects silver, if the coiners have mixed more than islawful with the gold; or copper, if the coiners have alloyed with the gold orsilver more of it than is allowable. I will explain all these methods with theutmost care that I can.

*We have but little record of anything which could be called “ assaying ” among theGreeks and Romans. The fact, however, that they made constant use of the touchstone(see note 37, p. 252) is sufficient proof that they were able to test the purity of gold and silver.The description of the touchstone by Theophrastus contains several references to “ trial ”by fire (see note 37, p. 252). They were adepts at metal working, and were therefore familiarwith melting metals on a small scale, with the smelting of silver, lead, copper, and tinores (see note 1, p. 353) and with the parting of silver and lead by cupellation. Consequently,it would not require much of an imaginative flight to conclude that there existed some systemof tests of ore and metal values by fire. Apart from the statement of Theophrastus referredto, the first references made to anything which might fill the role of assaying are from theAlchemists, particularly Geber (prior to 1300), for they describe methods of solution,precipitation, distillation, fusing in crucibles, cupellation, and of the parting of gold and silverby acid and by sulphur, antimony, or cementation. However, they were not bent on