- Thumbnail, 2.4 x 1.7 x 1.7 cm
- Miyake Island (Miyake-jima), Izu Archipelago, Tokyo Prefecture, Japan
Anorthite is the calcium-rich end member of the albite-anorthite feldspar series. This old-time thumbnail is from a classic Japanese locality - Miyake Island and is a floater cluster of sharp, grayish-white anorthite crystal partially coated with a film of blackish glassy lava. Miyake Island is a small island with an active volcano and is famous as the classic locality for anorthite crystals, thousands of which were thrown out loose by the 1870 eruption and distributed in collections around the world. Accompanied by an expertly handwritten, faded label from an older collection. The collection this came out of was a museum stash dating to prior to World War I.