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Mineralpedia Details for Eastonite

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Eastonite

Eastonite

Eastonite is a mica group member phyllosilicate and is monoclinic. It is an "ordinary (True or Common) Mica - Trioctahderal. One half of the (T) sites occupied by Al. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Ideally all the Mg in the (M) sites and is actually in the Biotite series, yet is light in color. Previously thought to be a mixture of phlogopite and a new serpentine (AM Feb. '87 v. 72). Per Lauf (Coll. Guide to Mica Group Minerals) "considered by some author's to be aluminous variety of phlogopite.."

Only four localities worldwide (Mindat).

Formula
KAlMg2(Si2Al2)O10(OH)2 
Crystal System
Monoclinic 
Class
Monoclinic - Prismatic 
Hardness
WebMineral
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Mindat
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Eastonite from Williams quarry, Northampton Co., Pennsylvania, United States

Eastonite
            from Williams quarry, Northampton Co., Pennsylvania, United States
Special Info
Type Locality

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. One half of the (T) sites occupied by Al. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Ideally all the Mg in the (M) sites and is actually in the Biotite series, yet is light in color. Previously thought to be a mixture of phlogopite and a new serpentine (AM Feb. '87 v. 72). Per Lauf (Coll. Guide to Mica Group Minerals) "considered by some author's to be aluminous variety of phlogopite.."

Only four localities worldwide (Mindat).

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