Clear grey-blue celestine crystal crust from Madagascar
Category Sulfate minerals
Chemical formula SrSO4 sometimes contains minor calcium and/or barium
Strunz classification 07.AD.35
Crystal symmetry Orthorhombic 2/m 2/m 2/m dipyramidal
Unit cell a = 8.359 Å, b = 5.352 Å, c = 6.866 Å; Z = 4
Color Colorless, white, pale blue, pink, pale green, pale brown, black
Crystal habit Tabular to pyramidal crystals, also fibrous, lamellar, earthy, massive granular
Crystal system Orthorhombic
Cleavage Perfect on {001}, good on {210}, poor on {010}
Fracture Uneven
Tenacity Brittle
Mohs scale hardness 3 - 3.5
Luster Vitreous, pearly on cleavages
Streak white
Diaphaneity Transparent to translucent
Specific gravity 3.95 - 3.97
Optical properties Biaxial (+)
Refractive index nα = 1.619 - 1.622 nβ = 1.622 - 1.624 nγ = 1.630 - 1.632
Birefringence δ = 0.011
Pleochroism Weak
2V angle Measured: 50° to 51°
Dispersion Moderate r < v
Ultraviolet fluorescence Short UV=yellow, white blue, long UV=yellow, white blue
References [1][2][3]

Celestine or celestite[4] (SrSO4) is a mineral consisting of strontium sulfate. The mineral is named for its occasional delicate blue color. Celestine is the principal source of the element strontium, commonly used in fireworks and in various metal alloys.


Celestine from the Machow Mine, Poland.

Celestine occurs as crystals, and also in compact massive and fibrous forms. It is mostly found in sedimentary rocks, often associated with the minerals gypsum, anhydrite, and halite.

The mineral is found worldwide, usually in small quantities. Pale blue crystal specimens are found in Madagascar.

The bodies of the protozoan Acantharea are made of celestine, unlike those of other radiolarians which are made of silica.

In carbonate marine sediments, burial dissolution is a recognised mechanism of celestine precipitation [5]


Celestine geode section
Inside the Crystal Cave geode in Ohio

Celestine crystals are found in some geodes. The world's largest known geode, a celestine geode 35 feet (10.7 m) in diameter at its widest point, is located near the village of Put-in-Bay, Ohio, on South Bass Island in Lake Erie. The geode has been converted into a viewing cave, Crystal Cave, with the crystals which once composed the floor of the geode removed. The geode has celestine crystals as wide as 18 inches (46 cm) across, estimated to weigh up to 300 pounds (135 kg) each.

See also


  1. Handbook of Mineralogy
  2. Mindat.org
  3. Webmineral data
  4. Nickel, Ernie.; Nichols, Monte. Mineral Names, Redefinitions & Discreditations Passed by the CNMMN of the IMA, Materials Data, 2004, p. 26. Celestine is the approved name for this mineral by the International Mineralogical Association Commission on New Minerals and Mineral Names (CNMMN). Although celestite finds frequent usage in some mineralogical texts, the name has been discredited as a valid mineral name by this organization.
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