BOOK VI
	A gem, as I have said, is exceptionally hard and transparent, as the diamond and smaragdus, or it is exceptionally beautiful because it is adorned with pleasing or variable colors as most species of jaspis. Trans­parency, unusual beauty of color, luster and brilliancy are, in great part, responsible for the value. However, even though some congealed juices such as salt, nitrum, alumen and atramentum sutorium are transparent they cannot be numbered among the gems because they are not hard and for the same reason gypsum and silver-colored mica which are also trans­parent. Nor the stones which melt in a fire although they have the same colors and are as transparent as gems. Tephrites, diphyes, enorchis, crypto-petra, tecolithos and similar stones are not classed as gems because they cannot be cut, they are not brilliant, nor are they adorned with beautiful or variable colors. For the same reasons asbestos, bostrychites, corsoides, polia and spartopolios which are names for asbestos are not regarded as gems. On the other hand hematite, lysimachia, arabica, alabastrites, meroctes, obsidianus, siderites and similar stones are classed as gems be­cause these stones as well as small fragments of marble are cut and pol­ished and to a limited extent set in rings. However we will not treat these minerals here. A small piece of hematite does not differ from a large mass either in color or porperties, only in size. Lysimachia is the same as Rho-dian marble; arabica, as Arabian marble; capnites, as marble with smoky spirals; alabastros, as alabastrites; exhebenus, as samius lapis; obsidiana which is also called samothracia, as obsidianus; meroctes, as thyites; and siderites, as basaltes. I have already discussed amber, which Pliny correctly classifies as a gem, in Book IV as well as those minerals which are either amber or at least consist of bitumen. In this genus are anatachates, aroma-tites, myrrhites, zanthenes, baptes, atizoe, catochites and lipare. I have dis­cussed coral which Pliny calls gorgonia and, as it appears to me, crocallis. I have mentioned spongites, syringites and phycites and therefore will say nothing about them here. Certain minerals having the distinct qualities of gems do not deserve to be placed among the gems because they do not form definite species, for example, it falls to many gems to be distinguished by one line or more. Thus jaspis is called grammatias when one line runs through it and poly-grammos when there are many lines running through it. Any other gem could be called by these same names if marked the same way. If a white line runs through the middle of any colored gem this is called mesoleucos, if a black line, mesomelas, if a green line it could be called mesochloros and if of some other color, by any similarly appropriate name. When a thin white line runs from the top to the base of a gem it is called perileucos, with a black line it could be called perimelas and with a line of another
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