Heulandite-Na

heulandite-Na

chalcedony

mordenite

quartz

Images

Formula: (Na,Ca,K)₅(Si₂₇Al₉)O₇₂.22H₂O
Tectosilicate (framework silicate), heulandite subgroup, zeolite group, forms a series with clinoptilolite-Na
Crystal System: Monoclinic
Specific gravity: 2.2 measured, 2.12 calculated
Hardness: 3 to 3½
Streak: White
Colour: White, reddish white, greyish white, brownish white, yellow
Environments

Basaltic cavities

Heulandite-Na is a low temperature zeolite found in a wide variety of geologic environments: volcanic rocks, metamorphic rocks, pegmatites, tuffs and deep-sea sediments (Webmin).

Localities

At the type locality, an Unnamed pit, Challis, Bay Horse Mining District, Custer County, Idaho, USA, heulandite-Na occurs as complete fillings of small vesicles in the rock, as drusy linings of cavities, and as thin crusts forming the first lining of cavities later filled with mordenite, chalcedony or quartz (Mindat).
Back to Minerals