Celestite
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/14730981@N08">James Petts</a> from London, England (CC BY-SA 2.0)
Mineral NameCelestite
Chemical FormulaSrSO4
Mohs Hardness3.5
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
Cleavageperfect on {001}, good on {210}, fair on {010}
Fractureuneven
Specific Gravity3.96
Colorswhite, off-white, pale blue, colorless
Transparencytranslucent
Type LocalityMadagascar, Ohio (USA), Sicily (Italy)
Mineral GroupSulfates
Usesstrontium ore, fireworks, signal flares, ceramics, collector
Associated Mineralsgypsum, anhydrite, calcite, dolomite, sulfur
Raritycommon
Description
This specimen displays white to off-white celestite crystals with a vitreous luster, embedded within a rough, yellowish-brown matrix. The crystals show distinct cleavage planes, giving them a somewhat blocky or layered appearance.
Geological Context
Celestite commonly forms in sedimentary rocks, particularly in evaporite deposits, limestones, and dolomites, often as a result of diagenetic replacement or precipitation from hydrothermal solutions. It is frequently found lining geodes and vugs.
