Inderite, also referred to as Lesserite, is a relatively rare borate mineral but extremely rare as a gem that is faceted. It’s very soft and tough to cut due to its softness and cleavage that is ideal. Inderite is formed in Borate deposits in arid regions.

You can find very areas which can be few Inderite can be located but only one source for gem quality crystals which is Boron, Kramer District, Kern County, California, USA.

Chemical Formula: MgB3O3(OH)5 · 5(H2O)
Hydrated Magnesium Borate Hydroxide
Molecular Weight: 279.85 gm
Composition: Magnesium 8.69 % Mg 14.40 % MgO
Boron 11.59 % B 37.32 % B2O3
Hydrogen 5.40 % H 48.28 % H2O
Oxygen 74.32 % O
  100.00 % 100.00 % = TOTAL OXIDE


Crystallography: Monoclinic – Prismatic
Crystal Habit: As long prismatic crystals with nearly square cross-section, to 30 cm; may be as aggregates of minute needles; reniform nodular, massive.
Twinning: None


Cleavage: Perfect on {010}, Good on {110}
Fracture: Irregular/Uneven
Tenacity: Brittle
Moh’s Hardness: 2.5 – 3.0
Density: 1.80 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive
Other: Insoluble in water. Readily soluble in warm, dilute HCl.


Color: Colorless to White, Pink
Transparency: Translucent to Transparent
Luster: Vitreous to Pearly on cleavages, Dull, Greasy
Refractive Index: 1.488 – 1.505  Biaxial ( + )
Birefringence: 0.0170
Dispersion: Weak; r > v
Pleochroism: None