Dachiardite

tectosilicate

pegmatite

Dachiardite is a series between three minerals:
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 200oC (Dana).

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