Nambulite is a very rare mineral first found at the Funakozawa Mine in the Kitakami Mountains of Japan and more recently found at the Kombat Mine near Tsumeb, Namibia. In contrast, an isotropic crystal includes all isometric crystals, and the velocity of light is equal in all directions. The chemical formula of Nambulite is (Li, Na)Mn4Si5O14(OH). Most Nambulite is opaque, occasionally translucent, very rarely transparent and only available as cabochons. There is a completely transparent, flawless crystal reported from the Namibian material but this is in a private mineral collection and not available for faceting. If there were any transparent, faceted gems, they would be extremely rare and very valuable. Nambulite has a very beautiful, very intense orange-red color.

Category: Inosilicate
Chemical Formula: (Li, Na)Mn4Si5O14(OH)
Crystallography: Triclinic – Pinacoidal
Crystal Habit: Crystals are prismatic to tabular crystals, to 8 mm; massive in veinlets.


Cleavage: [001] Perfect, [100] Distinct, [010] Distinct
Fracture: n/a
Tenacity: Brittle
Moh’s Hardness: 6.5
Density: 3.51 (g/cm3)
Radioactivity: Not Radioactive


Color: Reddish brown, orange-brown, reddish orange
Transparency: Transparent, Translucent to Opaque
Luster: Vitreous
Refractive Index: 1.707 – 1.730  Biaxial (+)
Birefringence: 0.023
Dispersion: Weak