Anorthite

Labradorite
Nain Complex, Labrador, Newfoundland and Labrador, Canada
© 2003 John H. Betts

Formula:    CaAl2Si2O8
System:  Triclinic   
Colour:  Colourless, reddish ...
Hardness: 6 - 6½
Member of: Feldspar Group
Name: From the Greek αν and oρθός, "not right angle" or "oblique", in allusion to the oblique triclinic form of the crystals.
Polymorph of:  Dmisteinbergite, Svyatoslavite

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Type Occurrence of Anorthite

Type Locality:  Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy
Year of Discovery:  1823

Occurrences of Anorthite

Geological Setting:  Mafic plutonic rocks

Physical Properties of Anorthite

Lustre:  Vitreous
Diaphaneity (Transparency):  Transparent, Translucent
Colour:  Colourless, reddish grey, white
Streak:  White
Hardness (Mohs):  6 - 6½
Tenacity:  Brittle
Cleavage:  Perfect
Perfect on {001}, less so on {010}, imperfect on {110}
Fracture:    Irregular/Uneven, Conchoidal
Density (measured):    2.74 - 2.76 g/cm3
Density (calculated):    2.76 g/cm3

Chemical Properties of Anorthite

Formula:    CaAl2Si2O8
Essential elements: Al, Ca, O, Si
All elements listed in formula:    Al, Ca, O, Si
Common Impurities: Ti,Fe,Na,K

Photo:

This sample is about 8x11 cm and is from Monzoni, Val di Fassa, Trentino-Alto Adige, Italy.

More Info >> Mindat: Anorthite

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Posted in: Minerals