http://b4hntuy3fimfh2227vf4f74emnya7p35i5brtqujs6leqvtclfwvjbqd.onion/doc/physics/diamonds-crookes/The%20Project%20Gutenberg%20eBook%20of%20Diamonds,%20by%20William%20Crookes..html
Thus, on
the one hand, it is the hardest substance
found in nature or fashioned by art. Its
reflecting power and refractive energy, on
the other hand, exceed those of all other
colourless bodies, while it yields to none in
the perfection of its pellucidity.”