Encyclopedia > Anorthite

Article Content

Anorthite

Anorthite is one of the plagioclase feldspars, an important group of minerals abundant in the Earth's crust. Anorthite's chemical formula is CaAl₂Si₂O₈.

Table of contents

3 Details

Mineralogy Anorthite is the calcium-rich endmember of the plagioclase system, the other endmember being albite[?] (sodium-rich). The range of intermediate compositions have varying ratios of calcium and sodium ions.

Occurrence Anorthite occurs in igneous and metamorphic[?] rocks. Its type localities[?] are Monte Somma and Valle di Fassa, Italy,

Details

Crystallographic system	Triclinic
Colours	Normally colourless or white, colourless in thin section.
Lustre	Vitreous
Hardness	6-6.5
Refractive index	1.51
Cleavage	3: 1 perfect, 1 good, 1 poor
Twinning	Multiple lamellar and Carlsbad twins[?]
Pleochroism	Yellow to dark green to transparent to opaque

See also

External link

WebMineral entry (http://webmineral.com/data/Anorthite.shtml)

All Wikipedia text is available under the terms of the GNU Free Documentation License

Search Encyclopedia

Search over one million articles, find something about almost anything!