Celsian belongs to the Feldspar Group. Celsian has the chemical formula BaAl2Si2O8. It was named after the Swedish astronomer and natural scientist, A. Celsius. — Photo: Shannon Heinle · CC0
Celsian
An uncommon barium feldspar found in barium-rich contact-metamorphic rocks, white to yellow and monoclinic.
Intro adapted from Wikipedia (CC BY-SA).
Celsian is an IMA-recognized mineral species in the silicate class, with the chemical formula Ba(Al₂Si₂O₈).
It crystallizes in the monoclinic crystal system (space group I2/c). It is a member of the Feldspar structural group.
Key properties: Mohs hardness 6–6.5; specific gravity 3.1–3.39; typically colorless or white; white streak; Vitreous luster; refractive index 1.588; optically biaxial.
IMA symbol Cls, grandfathered status — known before the IMA’s founding, named in 1895.
Found in amphibolite-grade, regional or contact metamorphic, Mn, Ba-rich rocks, some of which probably were submarine exhalatives.
It is found associated with Manganoan aegirine, manganoan biotite, paracelsian, jacobsite, hausmannite, rhodochrosite, rhodonite, rutile, hyalophane, barite, cymrite, taramellite, quartz.
The mineral was named to honor the Swedish astronomer and naturalist, Anders Celsius (1701–1744).
Collections: Collector Favorites, Rare & Remarkable.