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

Color

Colorless, white, light yellow, brown, reddish-brown, blue, gray

Crystal System

Monoclinic

Properties

Streak White

Hardness 6 - 6.5

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

Crystal Habits

Occurs as short tabular crystals and as long, slender prisms. Also occurs acicular, massive, and as crusts.

Additional Information

Composition Barium aluminum silicate, sometimes with some calcium and potassium.

In Group Silicates; Tectosilicates; Feldspar Group

Striking Features Heaviness and localities

Environment In barium-rich contact metamorphic rocks.

Rock Type Metamorphic

Varieties

Hyalophane

 -   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.

Noteworthy Localities

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.

Common Mineral Associations

Quartz, Barite, Aragonite, Plagioclase

Distingushing Similar Minerals

Other Feldspars - Considerably lighter in weight.

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