Sphene
Sphene | |
---|---|
Chemical composition | CaTiOSiO4 |
Crystal system | Monoclinic |
Habit | Wedge shaped, massive |
Cleavage | Distinct, prismatic |
Fracture | Conchoidal |
Hardness | 5.0-5.5 |
Optic nature | Biaxial + |
Refractive index | 1.880-2.099 |
Birefringence | 0.100-0.135 |
Dispersion | High, 0.051 |
Specific gravity | 3.45-3.55 |
Lustre | Resinous to sub-adamantine |
Pleochroism | Distinct to strong |
Sphene is the older name of this mineral wich refers to its crystalshape. Titanite is the universial name amongst mineralogists today and refers to its content of titanium. Greenovite is the name given to red or pink sphene. Gemologists use the name sphene for gem material titanite.
Sphene is isostructural with tilasite, malayaite and fersmantite.
Contents
Diagnostocs
Colour
Yellow, brown, green, reddish.
Streak
White.
Diaphaneity
Transparent to opaque.
Refractometer
nα = 1.843 - 1.950, nβ = 1.870 - 2.034, nγ = 1.943 - 2.110 with a birefringence of 0.100 - 0.192.
Optical nature: biaxial positive.
Polariscope
Due to its small to moderate 2V value (17-40°) a clear biaxial interference pattern may be seen (two melatopes visible in one image).
Pleochroism
Strong; colourless, greenish-yellow, reddish.
Spectroscope
Mean absorption lines: 586, 582.
Fluorescence
None (probably due to iron content).
Occurence
Sphene is a common and widespread mineral in many igneous rocks and metamorphic rocks. Associated minerals are pyroxene, amphibole, feldspar and quartz.
Habit
Wedge-shaped crystals that may show parting due to twinning. Less common massive or lamellar. Sphene is normally fine grained but occacionally forms large crystals.
Sphene may show some degree of metamictization.
Treatments
Sphene is changed to red or orange through heating.
Deposits
Myanmar, Sri Lanka, Brazil, Mexico, Russia and Austria
Sources
- Gems sixth edition (2006) - Michael O'Donoghue ISBN 0750658568
- Gemstones of the world 13th edition (2006) - Walter Schuman ISBN 1402740166
- Mineralogy second edition (2002) - Dexter Perkins ISBN 0130620998