Sunstone

The photo shows three polished stones in orange peach, with tiny glittering specks and faint lines inside. Sunstone is a feldspar, from the same family as moonstone and labradorite. The glitter is called aventurescence, and according to Geology.com, it comes from tiny flat plates of minerals inside the stone, all lined up in the same direction. When light hits them at the right angle, they all reflect it at once.

Those plates, according to Geology.com and Wikipedia, are usually made of copper, hematite or goethite. And according to Geology.com, there are three ways to see the flash: move the stone, move the light, or move your head. Anyone holding a sunstone usually tries all three.

The most famous sunstone in the United States comes from Oregon. According to Wikipedia, in 1987 it was named the official state gemstone, and according to GIA, its colors are completely natural, with no treatment. According to Geology.com, it is found there in basalt flows, and the US Bureau of Land Management has set aside an area where anyone can come, look for sunstone, and keep what they find. Perhaps the cheapest way to get a gemstone: just gas and a shovel.

But not every sunstone comes from Oregon. According to Geology.com, sunstone from India is thought to have hematite inclusions rather than copper, and a loupe can show the difference. And according to Wikipedia, in the early 2000s a red or green stone called "andesine" appeared on the market, looking like sunstone. After much debate, it turned out that most of those stones had been artificially colored by a copper diffusion process.

Keep in mind that sunstone is a little delicate. According to Geology.com, its hardness is about 6, and it has perfect cleavage in two directions, so it suits earrings and pendants better. If you want it in a ring, choose a setting that protects it.