Nambulite Value, Price, and Jewelry Information

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

Nambulite

The color of Namibian nambulite is a striking orange-red, very intense, and not really like any other gem I have seen. Cut stones would be both extremely rare and quite magnificent, perhaps bearing some similarities to rhodonite.

Nambulite Information

Data Value
Name Nambulite
Colors Reddish brown, orange-brown, orange.
Stone Sizes Gems up to about 10 carats could potentially be cut from Namibian crystals.
Formula NaLiMn8Si10O28(OH)2
Hardness 6.5
Cleavage Perfect 1 direction, distinct 1 direction
Crystallography Triclinic. Crystals prismatic, flattened, and wedge shaped.
Refractive Index 1.707-1.730
Birefringence 0.023
Dispersion Weak.
Luminescence No data.
Luminescence Present No
Absorption Spectrum Not diagnostic.
Pleochroism Weak.
Optics a = 1.707; β = 1.710; γ = 1.730. Biaxial (+), 2V= 30°.
Optic Sign Biaxial +
Luster Vitreous.
Specific Gravity 3.51
Transparency Transparent.

Optics: a = 1.707; β=1.710; γ=1.730.

Biaxial (+), 2V= 30°.

Occurrence: Nambulite is a rare mineral reported in crystals up to 8 mm long at the Tunakozawa Mine, Northeast Japan. These crystals are found in veins cutting manganese oxide ores. Much larger crystals, up to approximately 3 cm across, have more recently been found in Namibia, at the Kombat Mine, near Tsumeb. I have seen a completely transparent crystal in a private collection that would yield about 20-25 carats of flawless faceted gems, the largest of these perhaps 10 carats in weight.

Comments: The color of Namibian nambulite is a striking orange-red, very intense, and not really like any other gem I have seen. Cut stones would be both extremely rare and quite magnificent, perhaps bearing some similarities to rhodonite.

Name: After Professor Matsuo Nambu of Tohoku University, Japan, for his studies of manganese minerals.

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