Taaffeite

Taaffeite is very rare, and is unique in being the only gemstone not recognized as a new mineral species until it had been faceted. The first specimen was found by Count Taaffe in Ireland, in a jeweller’s box of stones.

It looked like spinel, had a pale mauve tinge, and was cushion-cut, but was eventually found to be a new, doubly refractive (rather than singly refractive like spinel) mineral. Since then, more specimens have been found; these range in hue from red to blue to almost colourless.

Taaffeite occurs in Sri Lanka, China, and the former USSR. No imitation taaffeites appear to exist.

Cause of Color :

Pink / Red: Chromium

Chemical Composition :

Oxide of beryllium, magnesium aluminium – BeMg3Al8O16 + Fe, Mn, Zn, Cr

Crystal System / Forms :

Hexagonal System / Pyramidal, bi-pyramidal and often truncated by basal pedion (hemimorphic)

Cuts & Uses :

Facetted cuts.

Dispersion : 0.019
Hardness : 8
Lustre : Vitreous
Magnification :

Crystals (spinel etc.), two phase inclusions, liquid fingerprints

Optic Character :

Anisotropic, D.R.; Uniaxial negative

Pleochroism : Weak
Refractive Index / Birefringence :

1.718 – 1.722 / 0.004

Simulants (with separation tests) :

Natural spinel (optic character), Idocrase (spectrum, S.G.), Sapphirine (R.I., S.G.), etc.

Sources :

Sri Lanka, Russia (Eastern Siberia), China

Spectrum :

Not characteristic

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