Celestine - SrSO₄

Habit: Colorless, white, pale blue, pink, pale green, pale brown or black. Well-formed crystals common, typically thin to thick tabular, lathlike or with equant cross-sections, or pyramidal; also fibrous, lamellar, earthy or massive granular forms. Vitreous luster, pearly on cleavages; transparent to translucent. White streak.

Environment: The most common strontium mineral. Of primary sedimentary origin, precipitated by migrating strontium-bearing groundwater or basinal brines in carbonate rocks, concretions and nodules. Also occurs in hydrothermal veins and mafic volcanic rocks.

Etymology: From the Latin caelestis, meaning "celestial," in allusion to its typical bluish color.

Celestine geodes up to 11 meters (35 ft.) in diameter formed near the U.S. village of Put-in-Bay, Ohio. The geode crystals can be as wide as 46 cm (18 in.) across and are estimated to weigh 135 kg (300 lb.) each. The geode cave was exposed when workers were digging a well for a winery.