Ettringite Value, Price, and Jewelry Information

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

Ettringite

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 Information

Data Value
Name Ettringite
Colors Colorless to light yellow, milky.
Crystallography Hexagonal; usually flattened hexagonal dipyramids; sometimes prismatic, fibrous.
Refractive Index 1.470-1.491
Luster Vitreous.
Hardness 2 - 2.5
Specific Gravity 1.77
Birefringence 0.021
Cleavage Perfect, rhombohedral
Stone Sizes Material 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
Luminescence Present No
Transparency Transparent to translucent.
Absorption Spectrum Not diagnostic.
Formula

Ca6AI2(SO4)3(OH)1224H2O

Pleochroism

None; colorless in transmitted light; dehydrates and turns white.

Optics

= 1.491; = 1.470. Uniaxial (-).

Optic Sign Uniaxial -

Series to Sturmanite.

Optics:  = 1.491; = 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.