Sunstone: glitter from the inside
A common rock-forming mineral that turns into a gem when millions of tiny metallic plates line up inside it.
Feldspar is the most common mineral group in the Earth's crust. Most of it is plain white, grey or pink rock. Sunstone is feldspar with a difference. As it cooled, tiny flat crystals of iron oxide, usually hematite, grew inside it in thin, parallel plates.
Turn the stone under a light and those plates flash all at once. Gemmologists call the effect aventurescence. It is the same word used for aventurine, and it comes from the Italian for "by chance", after a glass made by accident in a Venetian workshop.
Not all sunstone is the same mineral. Most of the sunstone in the bead and tumble trade is oligoclase from India, with an orange body and a soft shimmer. Oregon sunstone in the United States is a labradorite feldspar coloured and spangled by copper, and it is usually sold as faceted gems.
For a shop, sunstone is a warm, cheerful stone that is hard enough for bracelets, beads and tumbling. The sparkle is subtle in a bin and lively in the hand, so it rewards a good light and a customer who picks it up.
Millions of tiny metal plates, lined up like mirrors. That is the glitter in sunstone.
