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Analcime

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Analcime
Analcime with aegirine and natrolite from Mont Saint-Hilaire, Québec (size: 78 x 65 x 53 mm)
General
CategoryZeolite
Formula
(repeating unit)		NaAlSi2O6·H2O
Strunz classification9.GB.05
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupIbca
Identification
ColorWhite, colorless, gray, pink, greenish, yellowish
Crystal habitTypically in crystals, usually trapezohedrons, also massive to granular.
TwinningPolysynthetic on [001], [110]
CleavageVery poor [100]
FractureUneven to subconchoidal
Mohs scale hardness5 - 5.5
LusterVitreous
StreakWhite
Specific gravity2.24 - 2.29
Optical propertiesIsotropic; anomalously biaxial (-)
Refractive indexn = 1.479 - 1.493
Fusibility3.5
Other characteristicsWeakly piezoelectric; weakly electrostatic when rubbed or heated.
References[1]

Analcime or analcite (from the Greek analkimos - "weak") is a white, gray, or colorless tectosilicate mineral. Analcime consists of hydrated sodium aluminium silicate in cubic crystalline form. Its chemical formula is NaAlSi2O6·H2O. Minor amounts of potassium and calcium substitute for sodium. A silver-bearing synthetic variety also exists (Ag-analcite).

Analcime is usually classified as a zeolite mineral, but structurally and chemically it is more similar to the feldspathoids. Analcime occurs as a primary mineral in analcime basalt and other alkaline igneous rocks. It also occurs as cavity and vesicle fillings associated with prehnite, calcite, and zeolites.

Locations

Well known locations for sourcing analcime include Croft Quarry in Leicestershire, UK; the Cyclopean Islands east off Sicily and near Trentino in northern Italy; Victoria in Australia; Kerguelen Island in the Indian Ocean; in the Lake Superior copper district of Michigan, Bergen Hill, New Jersey, Golden, Colorado, and at Searles Lake, California in the United States; and at Cape Blomidon, Nova Scotia and Mont Saint-Hilaire, Quebec in Canada; and in Iceland.

See also

References

  1. ^ Handbook of Mineralogy, Mineral Data Publishing
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