Soft, fragile, and hard to cut, celestite or celestine is seldom seen in collections. Large, clean faceted celestites are very rare. These gems are usually colorless or pale blue, but rare orange, green, yellow, and red shades have also been found.
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.|
|Specific Gravity||3.97 – 4.00|
|Birefringence||0.009 – 0.012|
|Cleavage||Perfect 1 direction, good 1 direction.|
|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. Biaxial (+), 2V = 50°|
|Etymology||From the Latin coelestis for “celestial,” in allusion to the delicate and lovely pale blue color often displayed by this mineral.|
|Occurrence||Celestite occurs in sedimentary rocks, especially limestones; it is also found in hydrothermal vein deposits, sometimes in igneous rocks.|
|Inclusions||Single phase, liquid inclusions; partially healed fractures.|
While transparent crystals aren’t rare per se, facetable gem-quality material is quite rare. Faceted gems show little fire.
Gems from Madagascar have refractive indices as follows: a = 1.619; γ = 1.631.
Blue gems may fade because of heat or light. Irradiation may restore the color.
Canada produces rare orange crystals. Tsumeb, Namibia also yields gem-quality material.
- United States: California; Colorado; Strontian Islands, Lake Erie, Michigan (gemmy material); Chittenango Falls, New York; Clay Center, Put-in-Bay, Ohio; Lampasas, Texas (gemmy blue material).
- Austria; Egypt; Bristol, England; France; Germany; Italy; Madagascar; San Luis Potosi, Mexico; Russia; Girgenti, Sicily; Switzerland; Tunisia.
Celestite gems, usually colorless or pale blue, typically weigh under three carats. Such stones often receive step cuts. However, some gems are known in the 30-carat range. Large, transparent crystals may be found and cut.
Put-in-Bay, Ohio boasts the Crystal Cave, “the world’s largest geode.” Converted into a cave, the 35′ wide geode contains celestite crystals up to 18” across.
- Devonian Group (Calgary, Alberta, Canada): 20.1 cts (blue, Madagascar).
- National Museums of Canada (Ottawa, Ontario): 3.11 cts (orange step cut, Ontario, Canada).
- Private collection: 2.98 cts (blue, New York)
Due to its softness, perfect cleavage, and light sensitivity, this gem makes a better collector’s item than a jewelry piece. Celestites also have great heat sensitivity. Since jeweler’s torches can easily exceed 200° C (392° F) and cause the stone’s colors to fade, be wary if you take a jewelry piece to be repaired. Consult our gemstone jewelry cleaning guide for more recommendations.