Chemical Composition: CaTiSiO
5 (Calcium titanium silicate)
Mohs' Hardness: 5-5.5
Specific Gravity: 3.52-2.54
Cleavage: Perfect
Refractive Index 1.885-2.050
Double Refraction: +0.105 to +0.135
Dispersion: 0.051
Sphene is a soft gemstone which can be found in several places the world over. It forms it wedge shaped crystals and, because of this, is named after the Greek word for 'wedge'. It is the gem quality version of Titanite. The two stones are the exact same, except for their lustre and their transparency. Sphene is a gem, with a adamantine lustre and is transparent/translucent. Titanite, on the other hand, is rougher, very opaque stone and lacks such a vitreous lustre. Sphene can be colored red, yellow, brown or orange, whereas titanite is usually grey, but can be black or a dark reddish-brown.
Sphene is found in a wide variety of geologic areas. It has been found as an accessory constituent of igneous rocks such as granite, syenite, trachyte and phonolite, as well as in gneiss, schist and limestone. It can also be found in low temperature hydrothermal vents and can sometimes be discovered in alluvial sands. Geographically, sphene can be seen in the Kola Peninsula in northwestern Russia, the Swiss Alps, Ontario, Genoa in Italy, New York, New Jersey and Pennsylvania.
Large masses of the stone are used as an ore of titanium. Sphene is sometimes forged into cabochons or jewelry. Since the stone is so soft, one would think the jewelry it is made into is not so expensive. However, sphene does contain a bright "fire" inside due to its coloration and its high refraction and dispersion. The high refraction causes light to "bounce" off the stone and its high level of dispersion breaks up the light, similarly to a prism, but not so effectively.
Sources:
Precious Stones, by Dr. Max Bauer. Charles E. Tuttle Company: Rutland Vermont and Tokyo, Japan, 1969
Gemstones of the World, by Walter Schumann. Sterling Publishing Co., New York, 1979
Simon and Schuster's guide to Rocks and Minerals, Simon and Schuster Inc. New York, 1978
http://www.24carat.co.uk/sphene.html
view-source:http://209.51.193.54/minerals/silicate/sphene/sphene.htm
http://2.1911encyclopedia.org/S/SP/SPHENE.htm