Starkeyite

Starkeyite is a rare mineral composed of magnesium sulfate heptahydrate, with the chemical formula MgSO4·7H2O. It is a hydrated salt that typically forms as efflorescent crusts or needle-like crystals. Starkeyite is known for its softness and solubility in water.

The mineral was first discovered in 1889 and named after Captain Starkey of Utah, who collected the initial specimens. It is often found in arid or semi-arid environments, particularly in playa lake deposits, saline soils, and efflorescences on mine dumps or weathered rocks. Starkeyite forms under conditions where magnesium sulfate solutions are exposed to evaporation.

Commonly associated minerals include other sulfates like epsomite and hexahydrite, as well as halite. Its pale color, ranging from white to grayish or yellowish, and its tendency to disintegrate upon exposure to humid air are characteristic features. Due to its solubility, starkeyite is not considered a particularly stable mineral and can readily transform into less hydrated forms or dissolve entirely. Its rarity and ephemeral nature make it of interest primarily to mineral collectors and geologists studying evaporite environments.