Mineralpedia Details for 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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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).