The rarest things in the world, next to a spirit of discernment, are diamonds and pearls. – Jean de la Bruyere, translated from French

There are many sham diamonds in this life which pass for real, and vice versa. – William Makepeace Thackeray

Proverbs are mental gems gathered in the diamond districts of the mind. – William R. Alger

[T]he diamond and other precious stones are focuses of light, and essences of colour which seem expressly created to ornament on a small scale the human body with all the splendours which adorn the universe on a large scale. – Charles Blanc, Art in Ornament and Dress, 1875