Sphene gemstone

by Manisha G

image of sphene gemstoneChemical composition: Silicate of titanium and calcium.

Crystal characteristics: Monoclinic system. Wedge shaped crystals.

Varieties: Yellow, brown or green.

Physical properties: Hardness- 5.5; S.G-3.52 to 3.54; Lustre – Sub-admantine.

Refraction: Double, biaxial positive; R.I. – 1.885-1.990 to 1.915-2.050, too high for the stones to be tested on the refractometer.

Birefringence: 0.105 to 0.135 Transparent.

Spectrum: Rare earth spectrum of Didymium (5800A°)

Dichroism: Very strong, Dispersion: very high, “dispersion” in pale yellow stones exceed that of diamonds.

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