Sphene
Sphene is a very rare calcium titanium silicate that is hardly ever seen in jewelry or collections
Sphene Description
Sphene is a very rare calcium titanium silicate that is hardly ever seen in jewelry or collections. Sphene is also called titanite, which derives from the fact that it is an ore of titanium. The name sphene comes from the Greek word for wedge, which describes the shape of the ends of sphene crystals. Sphene has been prized for many years, mostly for its high amount of fire, however its scarcity always prevented it from becoming well known. Now however, new sources of the stone are being found, and we are starting to see it on the market more often. Most of the sphene we see today comes from Brazil and Madagascar, and some comes from Austria and Switzerland. Sphene is usually very small, as gems of more than two carats are almost impossible to find. The Smithsonian Institution in Washington DC has a collection of yellow sphene from Switzerland, that are arranged in a necklace.
Sphene is quite unusual and beautiful. It actually has a brilliant fire greater than that of diamonds, however it is soft and fragile, rating only a 5.5 on the hardness scale. Because of its fragility, sphene is never used for rings, however it is suitable for pendants, brooches, and earrings. Sphene is appealing not only because of its fire, but also because of its diamond like, adamantine luster, as well as its strong pleochroism, apparent in the colored stones. This pleochroism shows three different colors; colorless, greenish-yellow and brownish yellow. Sphene can be brown, grass green, golden yellow, greenish-yellow, yellow-brown, or sometimes gray or nearly black. Faceted stones have extremely high fire and rich colors. These crystals are often twinned and are best cut as brilliant or mixed cuts, so as to show the crystal’s beautiful fire in the best possible way. Sphene is usually transparent to translucent, though occasionally, it can be nearly opaque.Sphene is widely distributed as an accessory mineral, particularly in coarse-grained igneous rocks such as syenite, nepheline syenite, diorite and granodiorite. Sphene occurs similarly in cavities in metamorphic rocks such as gneisses, schists, granite, and some metamorphosed limestone. High quality sphene is found in Gilgit, northern Pakistan; the Eifel Mountains, Rhineland-Palatinate, in western Germany; Mount Vesuvius, Naples, in southern Italy; the Kola Peninsula, in northern Russia; Vastmanland, Sweden; Haliburtn County and Hastins County, in Ontario, Canada; and in the United States, around Orange County, New York, and Sussex County, New Jersey. Sphene can also be found in various other locations around Canada, Germany, Italy, Norway, Pakistan, Russia, Sweden, the United Kingdom, the United States, Burma, Austria, Switzerland, Madagascar, Mexico and Brazil.
Colour: Reddish brown, gray, yellow, green, or red
Crystal habit: Flattened wedge-shaped crystals, also massive
Twinning: Contact and penetration on {100}, lamellar on {221}
Cleavage: Distinct on [110], parting on {221}
Fracture: Sub-conchoidal
Mohs scale hardness: 5 to 5.5
Luster: Subadamantine tending to slightly resinous
Streak: Reddish white
Diaphaneity: Translucent to transparent
Specific gravity: 3.48 to 3.60
Optical properties: Biaxial (+)
Refractive index: na = 1.843 - 1.950
nß = 1.870 - 2.034
n? = 1.943 - 2.110
Birefringence: d = 0.100 - 0.160
Pleochroism: Strong: X = nearly colorless; Y = yellow to green; Z = red to yellow-orange
2V angle: 17 to 40° (measured)
Dispersion: r > v strong
Other characteristics: Radioactive - may be metamict
