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9 : SILICATES (Germanates) F : Tektosilicates without zeolitic
H2O B : Tektosilicates with additional anions 30
: Helvite Group, Danalite-Genthelvite Series, Danalite-Helvite
Series, Genthelvite-Helvite Series
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Color: |
Red,
Pink, Colourless, White, Yellow, pale Green to Emerald
Green; darkens to Brown and Black on
weathering |
Type
Locality: |
West Cheyenne Canon, Cheyenne District (St. Peters
Dome District), El Paso Co., Colorado, USA |
Genthelvite is an extremely rare mineral
and gem that forms a mineral series with Helvite and
Danalite. Genthelvite is a member of the Helvine
Group
of minerals that also includes Danalite, Genthelvite, Helvine and Tugtupite. Genthelvite was discovered in Cheyenne Canyon, El Paso
County, Colorado, USA in 1944 and has since been
found in several other locations around the world. Gems
are usually very small, less than a quarter carat, and
included. Colors include colorless, yellow, green, pink
to red and may darken to brown and black from weathering.
The
most notable locations for gem quality crystals are
Poudrette quarry Mont Saint-Hilaire, Rouville County, Québec, Canada;
Bakstevalåsen, Gunhildrud, Øvre Eiker, Buskerud,
Norway; Zagi Mountain, Mulla Ghori, Khyber Agency,
Federally Administered Tribal Areas (FATA), Pakistan; West Cheyenne Canyon,
near St. Peters Dome, El Paso County, Colorado, USA.
These locations produce only very small crystals.
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