|
TRANSLATION
|
||
|
|
||
|
ON STONES
Of the substances formed in the ground, some are made of water and some of eardi. The metals obtained by mining, such as silver, gold, and so on, come from water; from earth come stones, including the more precious kinds, and also the types of earth that are unusual because of their color, smoothness, density, or any other quality. As the metals have been discussed in another place, let us now speak about the stones.
In general we must consider that all of them are formed from some pure and homogeneous matter as a result of a conflux or percolation, or because the matter has been separated in some other way, as has been explained above. For perhaps some are produced in one of these ways, and some in the other way, and others in a different manner. Hence they gain their smoothness, density, brightness, transparency, and other such qualities, and the more uniform and pure each of them is, the more do these qualities appear. In general, the qualities are produced according to the accuracy with which the stones are formed and solidified.
Some things are solidified through heat, others through cold. And probably there is nothing to prevent some kinds of stones being formed by either of these two methods, although it would seem that all the types of earth are produced by fire, since things become solid or melt as a result of opposite forces. There are more peculiarities in stones; for most of the differences in the types of earth concern color, tenacity, smoothness, density, and so on, but in other respects the differences are rare.
Stones, however, have these differences and in addition there are others that depend on their power of acting on other substances, or of being subject or not subject to such action. For some can be melted and others cannot, some can be burnt and others cannot, and there are other differences of this kind. And some show a number of differences in the actual process of being set on fire and burnt, and some, like the smaragdos,1 can make the
1 A green stone, mentioned again in sees. 8, 23, 24, 25, id, 27, 35. The usual English translation is "emerald," but this is not the exact meaning of the word. For the identification of this stone, see Commentary, sees. 23 and 24.
|
||
|
|
||
|
' 45 '
|
||
|
|
||