Top lustre multicolour sphene        Yellow-green VS Sphene         Bright, neon-green Sphene crystal        very gemmy with good lustre,
                                                                                                                from Tanzania 62 carats, 3.5 x 2.5 x 0.9 cm
Crystal system:    Monoclinic            Hardness:        5,0 – 5,5
Density (S.G.):    3,54 – 3,55            Cleavage:        Distinct, prismatic
Streak:    White            Birefringence:        0,100 – 0,135
Dispersion:    High, 0,051            Lustre:            Resinous to sub-adamantine
Pleochroism:    Distinct to strong        Refractive index:    1,880 – 2,099
Colours:     Yellowish green, green, yellow, brown, reddish, colourless, grey and occasionally pink or black
Occurrence:    Sphene is widely distributed as an accessory mineral in intermediate and felsic plutonic rocks, pegmatites and alpine veins, particularly in coarse-grained igneous rocks such as syenite, nepheline syenite, diorite and granodiorite. It occurs similarly in schists or gneisses and in some metamorphosed limestones. The mineral is associated with amesite, apatite, feldspar, iron ore, pyroxene, quartz and zircon, as well as the rare earth metals cerium and yttrium. Sphene can also be found as detritus within sedimentary deposits.
Habitat:    Flattened 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 metamictisation (this means that the original crystal structure has been broken down and turned amorphous due to radiation damage).
Composition:    Calcium titanium silicate – CaTiSiO5

Sphene takes its name from the Greek word sphenos that means wedge as it is typically found in wedge-shaped (sphenoid) crystals. It is sometimes known as titanite, mainly due to its high titanium content (24%), and its colour is generally green, yellow and light white, yet in some forms it can also be brown, reddish and even black. The name titanite is, however, mostly applied to the black or reddish-brown non-gem material. The usual colours are created by iron and rare-earth element impurities. Varieties of sphene are chrome sphene, the rarest and most valuable form of sphene, which is intense green (colour caused by chromium), and greenovite, an unusual reddish variety that occurs in India and Italy owing its rose-red colour to manganese (MnO) impurities.

Although sphene was discovered in 1795 and has thus been around for some time, it is virtually unknown to the general public. The recent discoveries of more deposits have helped to bring sphene back on the scene. Facet-grade sphene was found in Mulla Ghani Baba in Pakistan, in 2004. The colour of this sphene is medium to dark brown, and a significant ‘red flash’ was notable in the faceted gems. In Badadkshan, Afghanistan, sphene was also found in 2004. The colour of Afghan sphene is greenish yellow. India also produces fine sphene but Madagascar remains the main source for facet-grade sphene. Although brown stones from Madagascar can be large, the green stones are most cherished by gem collectors and connoisseurs. Sphene is also found in Myanmar, Sri Lanka, Brazil, Mexico, Canada, USA, Russia, Italy, China, Switzerland, Germany, Norway and Austria.

Sphene is a rare collector stone with an unusually high refractive index and an adamantine (diamond-like) lustre. In a well-polished gemstone, the lustre can approach or equal that of diamond, but sphene is notoriously difficult to polish well. What makes these gems so special is that they are gorgeously brilliant and fiery, as sphene’s dispersion (fire) is one of the highest of all gem materials and is higher than diamond. Faceted sphene therefore displays flashes in the same way a diamond does – only better. This special effect due to dispersion refers to the ability of the gemstone to break a beam of light apart into its spectral colours. Because of its high refractive index and excellent dispersion, a well-cut stone can display stunning brilliance.

Strongly coloured sphenes are also heavily pleochroic (display different colours when gem is turned in different directions) and a wide variety of colours are displayed in good quality specimens. A unique characteristic of sphene is birefringence (double refraction), meaning that light splits into two rays as it passes through the gem, creating an array of colours that are remarkably beautiful. As a result, the back facets appear as double images, giving it a beautiful soft hazy appearance similar to the doubling seen in zircon or peridot. Sunlight is necessary to bring out the true brillance and colours of this gem – normal pictures just cannot do justice to their true beauty.

Sphene gemstones are usually smaller than two carats, so size is definitely a premium characteristic with this species. Colour and clarity are also important value factors, followed by the skill and artistry shown in faceting. There is a preference for stones that are lighter in tone, especially yellows, light oranges and greens, which can best exhibit sphene's magnificent dispersion. Chrome sphene is the most valuable type. In general, specimens with reasonably good clarity, (this stone is rarely even eye clean,) strong and attractive body colour and showing at least some dispersion command the best prices.

The relative low hardness of sphene however makes it susceptible to scratching and as it is very brittle, care should be taken to avoid hard hits against it. As a result, sphene’s safest use in jewellery is in the form of earrings, necklaces, pendants, or brooches rather than in rings for everyday wear. However, if it is set protectively and worn occasionally, it will be a spectacular addition to your jewellery case. Even if it is left as a loose gemstone, it still has dazzling beauty as a collector’s piece. Sphene should not be cleaned with steam or ultrasonics or come into contact with any acids.

References          Thomas, A. (2008) Gemstones: Properties, Identification and Use. London: New Holland

Compiled and written by Martine van der Westhuizen