Dachiardite Subgroup

dachiardite

ferrierite

zeolite

mordenite

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The dachierite subgroup includes:
Dachiardite-Ca: Ca₂(Si₂₀Al₄)O₄₈.13H₂O
Dachiardite-K: K₄(Si₂₀Al₄)O₄₈.13H₂O
Dachiardite-Na: Na₄(Si₂₀Al₄)O₄₈.13H₂O
These minerals are tectosilicates (framework silicates), zeolite group
Specific gravity: 2.14 to 2.21
Hardness: 4 to 4½
Streak: White
Colour: Colourless, white, pink, orange-red
Solubility: Decomposed by common acids
Environments:

Volcanic igneous environments
Pegmatites
Hydrothermal environments

Dachiardite is a hydrothermal zeolite that generally occurs in silica-rich environments, in late stages of pegmatites and in Si-rich volcanic rocks, but also in basalt and in hydrothermally altered tuffaceous sediments. It may be associated with mordenite, ferrierite and heulandite, which, like dachiardite, are all zeolites. At Yellowstone Park drill holes show temperatures of formation of 100 to 200^oC (Dana).

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