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The Mineral celsian

Celsian is a very rare barium-rich member of the feldspar group. This mineral is named after Anders Celsius (1701-1744), a famous Swedish astronomer and scientist who proposed the Celsius temperature scale. Celsian forms a solid solution series with Orthoclase, and the intermediary member is known as Hyalophane. Although sometimes viewed as a variety of Celsian, Hyalophane is scientifically classified as a distinct mineral species.
Chemical Formula BaAl2Si2O8
Composition Barium aluminum silicate, sometimes with some calcium and potassium.
Variable Formula (Ba,Ca,K)Al2Si2O8
Color Colorless, white, light yellow, brown, reddish-brown, blue, gray
Streak White
Hardness 6 - 6.5
Crystal System Monoclinic
Crystal Forms
and Aggregates
Occurs as short tabular crystals and as long, slender prisms. Also occurs acicular, massive, and as crusts.
Transparency Transparent to opaque
Specific Gravity 3.1 - 3.4
Luster Vitreous to greasy
Cleavage 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. The cleavage angle is about 90º.
Fracture Conchoidal to uneven
Tenacity Brittle
Complex Tests Soluble in hydrochloric acid
In Group Silicates; Tectosilicates; Feldspar Group
Striking Features Heaviness and localities
Environment In barium-rich contact metamorphic rocks.
Rock Type Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 3


 -  Intermediary member of the Celsian-Orthoclase mineral series. Although sometimes viewed as a variety of Celsian, Hyalophane is scientifically classified as a distinct mineral species.

Celsian is a very rare mineral. Localities include the Benallt Mine, Rhiw, Wales; Jakobsberg, Nordmark, Sweden; Candoglia, Piedmont, Italy; the Kaso Mine, Kanuma, Japan; Broken Hill, New South Wales, Australia; and Franklin, Sussex Co., New Jersey. Hyalophane localities are the Zagradski Potok Mine, Busovaca, Bosnia and Herzegovina; and the Lengenbach Quarry, Im Feld, Binntal, Switzerland.

Quartz, Barite, Aragonite, Plagioclase

Other Feldspars - Considerably lighter in weight.

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