112 BOOK V. 



classified as rich, of which each one hundred librae contains more than three 

 librae of silver. This quality comprises rudis silver, whether silver glance or 

 ruby silver, or whether white, or black, or grey, or purple, or yellow, or liver- 

 brilliancy, does not justify a more narrow rendering than " ironstone." Agricola (De Nat. 

 Fos., Book V.) gives elaborate descriptions of various iron ores, but the descriptions under 

 any special name would cover many actual minerals. The subject of pyrites is a most con- 

 fused one ; the term originates from the Greek word for fire, and referred in Greek and 

 Roman times to almost any stone that would strike sparks. By Agricola it was a generic 

 term in somewhat the same sense that it is still used in mineralogj', as, for instance, iron 

 pyrite, copper pyrite, etc. So much was this the case later on, that Henckel, the leading 

 mineralogist of the iSth Century, entitled his large volume Pyritologia, and in it embraces 

 practically all the sulphide minerals then known. The term marcasite, of medijeval Arabic 

 origin, seems to have had some vogue prior and subsequent to Agricola. He, however, puts 

 it on one side as merely a synonym for pyrite, nor can it be satisfactorily defined in much 

 better terms. Agricola apparently did not recognise the iron base of pyrites, for he says 

 (De Nat. Fos., p. 366) : " Sometimes, however, pyrites do not contain any gold, silver, copper, 

 " or lead, and yet it is not a pure stone, but a compound, and consists of stone and a substance 

 " which is somewhat metallic, which is a species of its own." Many varieties were known 

 to him and described, partly by their other metal association, but chiefly by their colour. 



Cadmia. The minerals embraced under this term by the old mineralogists form 

 one of the most difficult chapters in the history of mineralogy. These complexities reached 

 their height with Agricola, for at this time various new minerals classed under this heading 

 had come under debate. All these minerals were later found to be forms of zinc, cobalt, or 

 arsenic, and some of these minerals were in use long prior to Agricola. From Greek and 

 Roman times down to long after Agricola, brass was made by cementing zinc ore with 

 copper. Aristotle and Strabo mention an earth used to colour copper, but give no details. 

 It is difficult to say what zinc mineral the cadmium of Dioscorides (v, 46) and Pliny 

 (xxxiv, 2), really was. It was possibly only furnace calamine, or perhaps blende, for it was 

 associated with copper. They amply describe cadmia produced in copper furnaces, and 

 poinpholyx (zinc oxide). It was apparently not until Theophilus (1150) that the term 

 calamina appears for that mineral. Precisely when the term " zinc," and a knowledge of 

 the metal, first appeared in Europe is a matter of some doubt ; it has been attributed to 

 Paracelsus, a contemporary of Agricola (see note on p. 409), but we do not believe that author's 

 work in question was printed until long after. The quotations from Agricola given below, in 

 which zincum is mentioned in an obscure way, do not appear in the first editions of these 

 works, but only in the revised edition of 1559. In other words, Agricola himself only learned 

 of a substance under this name a short period before his death in 1555. The metal was 

 imported into Europe from China prior to this time. He however does describe actual 

 metallic zinc under the term conterfei, and mentions its occurrence in the cracks of furnace 

 walls. (See also notes on p. 409). 



The word cobalt (German kohelt) is from the Greek word cobalos, " mime," and its 

 German form was the term for gnomes and goblins. It appears that the German minars, 

 finding a material (Agricola's "corrosive material") which injured their hands and feet, con- 

 nected it with the goblins, or used the term as an epithet, and finally it became established 

 for certain minerals (see note 21, p. 214, on this subject). The first written appearance of the 

 term in connection with minerals, appears in Agricola's Ber^nannus (1530). The first 

 practical use of cobalt was in the form of zaffre or cobalt blue. There seems to be no mention 

 of the substance by the Greek or Roman writers, although analyses of old colourings show 

 some traces of cobalt, but whether accidental or not is undetermined. The first mention 

 we know of, was by Biringuccio in 1540 {De La Piroiechnica, Book 11, Chap, ix.), who did 

 not connect it with the minerals then called cohalt or cadmia. " Zaffera is another mineral 

 " substance, like a metal of middle weight, which will not melt alone, but accompanied 

 " by vitreous substances it melts into an azure col-iur so that those who colour glass, or 

 " paint vases or glazed earthenware, make use of it. Not only does it serve for the above- 

 " mentioned operations, but if one uses too great a quantity of it, it will be black and all other 

 " colours, according to the quantity used." Agricola, although he does not use the word 

 zaffre, does refer to a substance of this kind, and in any event also missed the relation 

 between zaffre and cobalt, as he seems to think (De Nat. Fos., p. 347) that zaffre came from 

 bismuth, a belief that existed until long after his time. The cobalt of the Erzgebirge was 

 of course, intimately associated with this mineral. He says, " the slag of bismuth, mixed 

 " together with metalliferous substances, which when melted make a kind of glass, will tint 

 " glass and earthenware vessels blue." Zaffre is the roasted mineral ground with sand, while 

 smalt, a term used more frequently, is the fused mixture with sand. 



The following are the substances mentioned by Agricola, which, we believe, relate 

 to cobalt and zinc minerals, some of them arsenical compounds. Other arsenical minerals 

 we give above. 



