basaltic cavities

Formula: Ba2(Si12Al4)O32.12H2O
Tectosilicate (framework silicate), zeolite group, barium mineral
Specific gravity: 2.41 to 2.47
Hardness: 4 to 5
Streak: White
Colour: Colourless, white, grey, pink, yellow, brown

Sedimentary environments (rarely)
Metamorphic environments
Basaltic cavities

Harmotome occurs in basaltic cavities associated with calcite and rarely natrolite. It has also been reported in tuff associated with calcite, laumontite and pyrite (DHZ 4 p398).

At Nisikkatch lake, Saskatchewan, Canada, harmotome occurs in veins in gneiss associated with hyalophane (variety of microcline) and albite (DHZ 4 p398).

In northern Italy harmotome occurs in graphite lenses in gneiss with quartz, sphalerite and galena (DHZ 4 p398).

In the Ural mountains, Russia, harmotome occurs in bauxite with kaolinite and halloysite (DHZ 4 p398).

At Snailbeach mine, near Minsterley, Shropshire, England, UK, harmotome occurs with calcite (RES p273).

At the Struy lead mines, Inverness, Scotland, UK, harmotome occurs in hydrothermal veins with sphalerite, baryte and calcite (DHZ 4 p398).

Common impurities: Na,Ca

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