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Mineralpedia Details for Vermiculite

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Vermiculite

Vermiculite

Phyllosilicate - Monoclinic - Not a Mica group member. But is micaceous. A member of the Montmorillonite-Vrmiculate group with 2:1 layering, meaning there are two (T) tetrahedral layers with an (M) octahedral layer in between. There is no (I) interlayer and the 2:1 layers are instead held together by weak Van der Waals bonds.

Requires Biotite, Chlorite, Hornbelnd and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.

Formula
Mg0.7(Mg,Fe3+,Al)6(Si,Al)8O20(OH)4ยท8H2
Crystal System
Monoclinic 
Crystal Habit
Lamellar, Scaly 
Cleavage
Perfect, None, None 
Luster
Vitreous - Dull 
Color
colorless, green, gray white, yellow brown 
Streak
greenish white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
1.5-2 
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Vermiculite from Iron mine, Kovdor Massif, Kola Peninsula, Russia

Vermiculite
            from Iron mine, Kovdor Massif, Kola Peninsula, Russia

Phyllosilicate - Monoclinic - Not a Mica group member. But is micaceous. A member of the Montmorillonite-Vrmiculate group with 2:1 layering, meaning there are two (T) tetrahedral layers with an (M) octahedral layer in between. There is no (I) interlayer and the 2:1 layers are instead held together by weak Van der Waals bonds.

Requires Biotite, Chlorite, Hornbelnd and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.

This is a nice cleavage plate.

More on rare mica minerals

Click thumbnail images for larger view.

Vermiculite from Palabora mine, Phalaborwa, Limpopo, South Africa

Vermiculite
            from Palabora mine, Phalaborwa, Limpopo, South Africa

Phyllosilicate - Monoclinic - Not a Mica group member. But is micaceous. A member of the Montmorillonite-Vrmiculate group with 2:1 layering, meaning there are two (T) tetrahedral layers with an (M) octahedral layer in between. There is no (I) interlayer and the 2:1 layers are instead held together by weak Van der Waals bonds.


Requires Biotite, Chlorite, Hornbelnd and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.

Larger cleavage plate to 8cm across.

Click thumbnail images for larger view.

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