Complete Works, Vol. V

lar. They are diversified in different ones, as will appear in what follows.

CHAPTER III.

On the transparency of stones according to more and less.

Of those stones which are transparent in greater or lesser degree, such as those that are called gems gemmae precious stones, as can be said in general, water is not the pure common matter. For those stones are certain glasses produced by the work of nature: for which reason they are also more subtle in mixture, and are of clearer transparency than the glasses of art: because art, although it imitates nature, yet cannot attain the full work of nature. A sign of that which we said, that water acted upon by dry heat or cold is the common matter of these stones, is that glasses are made from moisture of this kind, which is liquefied by the strongest fire from various ashes, whether of lead, or flint, or iron, or any other. That this moisture is water is shown by the fact that it is coagulated by cold, and liquefied when dissolved by violent dry heat. That it has been acted upon by dry, burned earth is proven by the fact that it is not liquefied except from ash through very intense roasting, just as we have said, and as is visibly shown in the art of glass-making arte vitraria glass-blowing, which is subordinate to alchemy alchimia alchemy: for the more subtle vapor in earth or in stone is sometimes contained by the surrounding matter, and, rolled within itself, becomes moist, as happens in a hot covered pot in which there is some water. And when moisture has thus been acted upon vehemently by the dry, and the force of the dry is constant in it, it is coagulated into a stone. But here we must not speak of the manner of the generation of stones, but rather of the matter of stones in general. Whether

their coagulation happens by cold or heat will be shown later. That water is the matter of this kind of stone is also shown: because in certain places in which there is a strong stone-generating virtue, water descending by rain, drop by drop or otherwise poured out, congeals into stone: for it first suffers from the dry earth, by the nature and operation of the place, and thus the proper matter of the stone is made. This is also shown from the multitude of transparency that is in such stones. For since the transparency of air and fire are not incorruptible, it must necessarily be that this transparency is from the transparency of water: therefore, their proper matter will be of the nature of water. That some of the Ancients, showing the matter of stones, say that something descends from running water which resides at the bottom, and this becomes stone, I do not approve, because that which descends from water is an earthy substance: and therefore frequently those stones which are generated from this do not receive water acted upon by earthy virtue as matter, but rather earth which has been acted upon by the virtues of water. A sign of this is that such stones are as frequently not transparent, but bounded, and are said to be very unworkable, but rather fragmentable, which are also called flints silices hard stones by the common people. Crystal crystallus quartz and beryl beryllus a clear silicate testify most strongly to these things that have been said, which have accepted almost the form of water ice, of which Aristotle original: "Aristoteles" said that they are made from water, with heat being universally removed.

Just as we said of the stones of which we made mention in the preceding chapter that their matter is earth, not simple, but acted upon by unctuous, viscous moisture: so also now it must be understood about these, that simple aqueous moisture cannot be the matter of transparent stones: because, as we have shown elsewhere, such moisture neither stands through boiling, nor is coagulated by dry heat, nor is frozen by any cold whatsoever: for which reason it is necessary