Celestite is seldom seen in collections, perhaps because faceted gems have little fire and are usually colorless or pale blue, rarely orange. Gems are soft and fragile, hard to cut, and cannot be worn with safety. Celestite is strictly for collectors; large, clean faceted gems are indeed rare, whereas transparent crystals per se are not.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Orthorhombic, Crystals common, usually tabular; also nodules, earthy, massive.|
|Colors||Colorless, white, gray, blue, green, yellow, orange, and red shades.|
|Luster||Vitreous; pearly on cleavage.|
|Density||3.97 – 4.00|
|Birefringence||0.009 – 0.012|
|Cleavage||Perfect 1 direction, good 1 direction; Fracture uneven. Brittle.|
|Stone Sizes||Celestine gems are usually under 3 carats and are generally colorless or pale blue, often step-cut. However, some gems are known in the 30 carat range, and there is no reason why large transparent crystals cannot be found and cut.|
|Luminescence||Blue in SW. Blue or dull yellow in LW. May phosphoresce blue-white.|
|Pleochroism||Weak, in shades of indigo blue, bluish green, and violet.|
OPTICS: a= 1.622 – 1.625; β = 1.624; γ= 1.631 -1.635.
Madagascar gems: a = 1.619; γ = 1.631.
Biaxial (+), 2V = 50°
OCCURRENCE: Celestite occurs in sedimentary rocks, especially limestones; it is also found in hydrothermal vein deposits, sometimes in igneous rocks. Clay Center, Ohio; Colorado; Chittenango Falls, New York; many localities in California. San Luis Potosi, Mexico; Bristol, England; Girgenti, Sicily; Madagascar; Germany; France; Austria; Italy; Switzerland; USSR; Egypt; Tunisia. Lampasas, Texas; gemmy material (blue) Put-in-Bay, Strontian Islands, Lake Erie: gemmy material. Tsumeb, Namibia: gem material Canada: orange crystals.
Devonian Group (Calgary, Alberta, Canada): 20.1 (blue, Madagascar) National Museums of Canada (Ottawa, Ontario): 3.11 (orange step-cut, Ontario, Canada) Private Collection: 2.98 (blue, New York)
COMMENTS: Celestite is seldom seen in collections, perhaps because faceted gems have little fire and are usually colorless or pale blue, rarely orange. Gems are soft and fragile, hard to cut, and cannot be worn with safety. Celestite is strictly for collectors; large, clean faceted gems are indeed rare, whereas transparent crystals per se are not.
NAME: Latin coelestis means celestial, in allusion to the delicate and lovely pale blue color often displayed by this mineral.