Zultanites

Zultanite is the trade name for gem diaspore, and it is bought for one thing: it changes color. In daylight it reads a soft kiwi green with a gold cast; step indoors under incandescent light and the same stone warms to champagne, sometimes to a definite pink. The shift is gradual rather than a switch, so it flickers as you move.

Diaspore has perfect cleavage and sits at Mohs 6.5 to 7, so it is cut carefully and worn thoughtfully — a bezel or a pendant over a daily ring. Judge one in two lights before you decide. Standard millimeter sizes.