Celestine (mineral)

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Celestine

Celestine - Sakoany deposit, Katsepy, Mitsinjo, Boeny, Madagascar.jpg

Clear grey-blue celestine crystals

General

Category Sulfate minerals

Formula

(repeating unit) SrSO4 sometimes contains minor calcium and/or barium

IMA symbol Clt[1]

Strunz classification 7.AD.35

Crystal system Orthorhombic

Crystal class Dipyramidal (mmm)

H-M symbol: (2/m 2/m 2/m)

Space group Pnma

Unit cell a = 8.359 Å,

b = 5.352 Å,

c = 6.866 Å; Z = 4

Identification

Color White, Pink, Pale green, Pale brown, Black, Pale blue, Reddish, Greyish; Colourless or lightly tinted in transmitted light

Crystal habit Tabular to pyramidal crystals, also fibrous, lamellar, earthy, massive granular

Cleavage Perfect on {001}, good on {210}, poor on {010}

Fracture Uneven

Tenacity Brittle

Mohs scale hardness 3.0–3.5

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°–51°

Dispersion Moderate r < v

Ultraviolet fluorescence yellow, white blue (both short & long UV)

References [2][3][4][5]

Celestine (the IMA-accepted name)[6] or celestite[1][7][a] is a mineral consisting of strontium sulfate (SrSO4). The mineral is named for its occasional delicate blue color. Celestine and the carbonate mineral strontianite are the principal sources of the element strontium, commonly used in fireworks and in various metal alloys.

Contents

1 Etymology

2 Occurrence

3 Geodes

4 Footnotes

5 See also

6 References

7 External links

Etymology

Celestine derives its name from the Latin word caelestis meaning celestial[8] which in turn is derived from the Latin word caelum meaning sky or heaven.[9]

Occurrence

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. On occasion in some localities, it may also be found with sulfur inclusions.

The mineral is found worldwide, usually in small quantities. Pale blue crystal specimens are found in Madagascar. White and orange variants also occurred at Yate, Bristol, UK, where it was extracted for commercial purposes until April 1991.[10]

The skeletons 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.[11] It is sometimes used as a gemstone.[12]

Celestine from the Machow Mine, Poland

Celestine from the Machow Mine, Poland

 

Celestine mineral on display at Yale's Peabody Museum

Celestine mineral on display at Yale's Peabody Museum

Geodes

Celestine crystals are found in some geodes. The world's largest known geode, a celestine geode 35 feet (11 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 (140 kg) each.

Celestine geodes are understood to form by replacement of alabaster nodules consisting of the calcium sulfates gypsum or anhydrite. Calcium sulfate is sparingly soluble, but strontium sulfate is mostly insoluble. Strontium-bearing solutions that come into contact with calcium sulfate nodules dissolve the calcium away, leaving a cavity. The strontium is immediately precipitated as celestine, with the crystals growing into the newly-formed cavity.[13][14][15]