Holtite Value, Price, and Jewelry Information

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This mineral was first noted in 1937 but was not described in detail until 1971. It has not yet been seen as a gem, but the high hardness would allow it be worn with no risk of scratching. Holtite is now considered to be a variety of dumortierite. The mineral comes from the one locality, and a cut stone would have to be considered a great rarity.

Holtite Information

Data Value
Name Holtite
Is a Variety of Dumortierite
Colors Cream white, buff, olive green, brownish.
Hardness 8.5
Cleavage Good 1 direction
Stone Sizes Could yield cabochons up to about 1 inch.
Formula Al6(Ta,Sb,Li)[(Si,As)O4]3(BO3)(O,OH)3 + Fe, Be, Ti, Mn, and Nb. Related to dumortierite.
Crystallography Orthorhombic. Compact pebbles of acicular crystals, 2-15 mm diameter. Needles often in parallel arrangement.
Refractive Index 1.743-1.761
Birefringence 0.015
Luminescence Dull orange in SW, bright yellow in LW.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
Pleochroism Distinct: yellow/colorless/colorless.
Optics = 1.743-1.746; β = 1.756-1.759; γ = 1.758-1.761. Biaxial (-), 2V= 49-55°.
Optic Sign Biaxial -
Luster Dull to resinous.
Specific Gravity 3.90
Transparency Translucent.

Optics: a= 1.743-1.746;  β= 1.756-1.759; γ= 1.758-1.761.

Biaxial (-), 2V= 49-55°.

Occurrence: Alluvial tin deposit near Greenoushes, Western Australia, associated with cassiterite.

Comments: This mineral was first noted in 1937 but was not described in detail until 1971. It has not yet been seen as a gem, but the high hardness would allow it be worn with no risk of scratching. Holtite is now considered to be a variety of dumortierite. The mineral comes from the one locality, and a cut stone would have to be considered a great rarity.

Name: After Harold E. Holt, prime minister of Australia from 1966 to 1967.

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