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Stilbite-Ca
Current inventory:  0 gems
 

Chemistry:  NaCa₄Al₈Si₂₈O₇₂·30(H₂O)

Discovered in 1801;   IMA status: Valid (pre-IMA; Grandfathered).
The name Stilbite is from the Greek word stilbe, meaning luster in allusion to its pearly luster. The Ca modifier was added by the Zeolite Committee due to its Calcium content.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.23-30

8 : Silicates
J : Tectosilicates (network) without anions unfamiliar to the tetraheders
23 : Zeolite group, Heulandite - Barium-Brewsterite series

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals typically thin tabular, to 14 cm; in fibrous, sheaf like or globular aggregates. Twinning: Cruciform and Penetration twins.

Physical Properties

Cleavage:

[010] Perfect

Fracture:

Concoidal

Tenacity:

Brittle

Moh's Hardness:

3.5 - 4.0

Density:

2.10 - 2.20 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, Colourless, Red, Light Yellow, Light to Dark Brown, Cream, Orange, Pink

Transparency:

Transparent to Translucent, Opaque

Luster:

Vitreous, Pearly

Refractive Index:

1.479 - 1.505  Biaxial ( - )

Birefringence:

0.0100 - 0.0130

Dispersion:

Weak

Pleochroism:

None

Occurances

Geological Setting:

A low-temperature hydrothermal mineral, in amygdules and cavities in basalts, andesites, and various metamorphic rocks. Formed in hot springs deposits, and as a cementing agent in some sandstones and conglomerates.

Type Locality:

Haüy mentioned occurrences in Iceland, Andreasberg in Harz, Alpes Dauphinoises and Norway, but no clear type-locality.

Year Discovered:

1801

View mineral photos:

Stilbite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Stilbite is a member of the Zeolite Group of minerals that includes over 40 minerals and these gem-type minerals: Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite-Na, Goosecreekite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite and Yugawaralite. Stilbite is not a rare mineral but it is rarely available as a faceted or cabochoned gem because its rarely transparent enough. Cabochoned gems do have a beautiful chatoyance and pearly luster and creamy orange gems are particularly beautiful. It is available from many sources worldwide but exceptional crystals from the Bombay, Poona, and Nasik districts, Maharashtra, India.
 

  
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