Ettringite Value, Price, and Jewelry Information


Ettringite
Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons

Ettringite is not generally facetable; any cut stone would be considered an extreme rarity. South African material has yielded minute stones, some of which may have been labeled sturmanite.

Ettringite Value

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Ettringite Information

DataValue
NameEttringite
Crystallography Hexagonal; usually flattened hexagonal dipyramids; sometimes prismatic, fibrous.
Colors Colorless; transparent to translucent, milky.
Luster Vitreous.
Hardness 2-2.5
Specific Gravity 1.77
Birefringence 0.021
Cleavage Perfect, rhombohedral.
Stone SizesMaterial from Ettringen and Franklin is microscopic. A 2.5 carat pale yellow ettringite was faceted from material found in the center of a mass of sturmanite from South Africa. This may be the largest known for the species.
Luminescence None
Spectral Not diagnostic
FormulaCa6AI2(SO4)3(OH)1224H2O
Pleochroism None; colorless in transmitted light; dehydrates and turns white.

Series to Sturmanite.

Optics:  o= 1.491; e= 1.470.

Uniaxial (-).

Occurrence: At type locality (Ettringen, Rhine Province, Germany) in cavities of metamorphosed limestone inclusions in alkaline igneous rocks. Also in metamorphosed limestones.

Ettringen, Germany: In tiny crystals.

Franklin, New Jersey: Minute crystals.

South Africa: Associated with sturmanite at the Jwaneng mine, near Hotazel. The sturmanite forms yellowish coatings, with ettringite cores.

Comments: Ettringite is not generally facetable; any cut stone would be considered an extreme rarity. South African material has yielded minute stones, some of which may have been labeled sturmanite.

Name: After the locality in Germany.