12. Heliotropium[359] ... receives the sun-light after the manner of a looking-glass, and reveals the eclipses of the sun, showing the moon passing under. In the case of this gem there is also a most manifest proof of the shamelessness of the magi, because they say its wearer is not visible if he takes an infusion of the plant heliotrope and in addition utters certain charms.
Chapter 8. On red gems.
1. ... The magi assert that [coral] resists thunder-bolts,—if it is to be believed.
Chapter 10. On white gems.
4. Galactites (milk-stone) is milk-white, and being rubbed it gives a white fluid that tastes like milk, and being tied on nursing mothers it increases the flow of milk. If it is hung on the necks of children it is said to create saliva, and it is said to melt in the mouth and take away the memory.
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.
Chapter 14. On glowing gems.