Chapter 13: On crystals

1. It is said that crystal glitters and is of a watery color because it is snow that has hardened into ice in the course of the years.... It is produced in Asia and Cyprus, and especially in the Alps of the north, where there is no hot sun even in summer. Therefore the ice itself is bared, and hardening through the years gives this appearance which is called crystal. This, being set opposite to the rays of the sun, so seizes upon its flame that it sets fire to dry fungi or leaves. Its use is to make cups, but it can endure nothing but what is cold.

2. _Adamas_ ... Though this is an unconquerable despiser of the steel and of fire, yet it is softened by the fresh, warm blood of stags, and then is shattered by many blows of an iron instrument.

3. It is said to reveal poisons as does amber (_electron_), to drive away useless fears, to resist evil arts.