Dunilite – Rare Olivine

Dunilite is a rare olivine group mineral with the corresponding chemical formula Magnesium, Iron, Manganese, Silicate (Mg,Fe,Mn)2SiO4. Long mistaken for green peridot, dunilite was identified in 2000 as a new gem variety from the olivine group. Dunilite- Discovered by Mr. Dunil Palitha Gunasekera in 1996.

Dunilite occurs in only one locality called, “Katukubura mountain” Kolonne, Sri Lanka. Dunilite can be found in colours light greenish-yellow to brownish green, the depth of colour being related to the iron content of the stone.

• Group: Olivine
• Crystal System: Orthorhombic
• Lustre: Vitreous
• Fluorescence: None
• Hardness: 6 1/2
• Fracture: Uneven
• Cleavage: None
• Specific Gravity: 3.48
• Optic Sign: Biaxial (-)
• Dispersion: 0.020
• Transparency: Transparent to translucent
• Habit: Tabular, rectangle shaped aggregate crystals.

• Refractive Index: a= 1.677, B=1.700, y=1.718 ( The refractive indices of dunilite are higher than peridot and sinhalite )

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Similarly looks with Faceted Stones:	Yellow chrysoberyl, Sinhalite
Tenacity:	Brittle

Might be confused with:	Peridot, Forsterite, Sinhalite
Birefringence :	0.041

Density:	3.48(g/cm3)
Radioactivity:	Not Radioactive

Dispersion:	Relatively Weak
Pleochroism:	Strong : Brownish Yellow/ Greenish Yellow

Usual Sizes:	0.05 to 1 carat
Occurrence:	In a huge calcite rock with black amphibole rocks