Sphene (Titanite)
Sphene (officially known as titanite) is a gemstone characterized by strong dispersion and "fire" (rainbow-like flashes of light). It was named after the Greek word "sphenos," meaning wedge, due to its wedge-shaped crystal habit. Even in small sizes, it can emit incredibly vivid brilliance depending on the cut, displaying a diverse range of colors including yellow, yellow-green, brown, and green.
Sphene, known for its impressive rainbow fire
Basic Information
| English Name | Sphene (Titanite) |
|---|---|
| Japanese Name | Kusabi-ishi (Wedge stone) |
| Chemical Composition | CaTi[O|SiO₄] |
| Crystal System | Monoclinic |
| Hardness | 5–5.5 |
| Specific Gravity | Approx. 3.53 |
Causes of Color, Varieties, and Trade Names
- Yellow to yellow-green and brown: Coloration due to Fe (iron).
- Green to yellow-green Vanadian sphene: A type containing V (vanadium).
- Deep green to olive green Chrom sphene: Coloration due to Cr (chromium).
- Specimens containing Mn (manganese) with a faint reddish tint are called "Greenovite," and those containing Y (yttrium) or rare earth elements (REE) with a pinkish tint are known as "Keilhauite."
- In the jewelry trade, it is sometimes marketed under the name "Titan Diamond" due to its intense brilliance.
Similar Stones and Related Information
Yellow to brown stones are often confused with sphalerite, which has an even higher refractive index; however, sphalerite can be distinguished by its lower hardness (3.5–4) and by being singly refractive, meaning it does not exhibit "doubling."
Small emerald-green cut stones resemble demantoid garnet (a type of andradite garnet), while yellow to yellow-green columnar crystals may resemble brazilianite.
The star effect (asterism) seen in star spinel is thought to be caused by needle-like sphene inclusions contained within the stone.
Distinctive Properties and Care
Sphene possesses very high birefringence, causing "doubling," where the edges of facets appear to double when viewed through the stone. Due to its high dispersion, it often shows even clearer rainbow fire than diamond.
Chemically, it is insoluble in HCl (hydrochloric acid) but soluble in H₂SO₄ (sulfuric acid), a property that can be useful during identification. On the other hand, it has distinct cleavage and frequent twinning, making it prone to breakage.
Care Tips: Because it is prone to splitting along its cleavage planes, it is not suitable for ultrasonic cleaning or exposure to strong impact. For jewelry, it is best worn in items like pendants that are subject to less impact, and it is also well-suited as a collector's loose stone.