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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)4ยท8H2O
- 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
- WebMineral
- View Vermiculite
- Mindat
- View Vermiculite
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.
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.
Vermiculite from Easton Talc quarry, Northampton Co., Pennsylvania, United States
Small to large (4cm), yellow plates of micaceous Vermiculite.
Although a monoclinic phyllosilicate, Vermiculite is not a mica group member. But it is micaceous. It is a member of the Montmorillonite-Vermiculate 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.
Vermiculate requires Biotite, Chlorite, Hornblend and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.