Indian sapphire, in the strict gemmological sense, refers to corundum mined within the borders of the Indian subcontinent, of which the Kashmir deposit in the western Himalayas is by far the most important. In looser trade usage, the term has at various times been used to describe sapphires of high colour saturation regardless of origin, and the buyer needs to be precise about which sense is meant in any given transaction.

The Kashmir deposit

The Kashmir sapphire deposit lies in the Padar region of the Zaskar range in Jammu and Kashmir, at elevations above 4,000 metres. The deposit was discovered in 1881 after a landslide exposed sapphire-bearing rock in the Sumjam (also spelled Soomjam or Sumjum) area, and the principal high-yield production ran from 1881 to roughly 1888 under the patronage of the Maharaja of Kashmir. After this initial seven-year window, output dropped sharply, and the deposit has produced only intermittently since, with no commercial-scale mining in recent decades.

The colour for which Kashmir sapphire is renowned is a velvety violetish blue with a slightly milky character that is described in the literature as a "sleepy" appearance. Lotus Gemology and GIA both attribute this character to fine inclusions, primarily fluid and short rutile needles in submicroscopic concentration, that scatter light gently across the stone and soften the otherwise deep saturation. The combination of saturation and softness is what makes Kashmir corundum the benchmark blue sapphire of the trade and the most consistently expensive blue sapphire on the secondary market.

Other Indian corundum

India has produced corundum from a number of other localities, though none has attained the trade prestige of Kashmir. The Karur district of Tamil Nadu has yielded blue and pink sapphire and ruby in alluvial and primary deposits since the late twentieth century. Orissa (now Odisha) has produced ruby and pink sapphire of variable quality. Star sapphires and rubies have been mined in small quantities from a number of South Indian localities. The Salem and Mysore regions also produce corundum, generally in lower-saturation colours.

None of this material is normally sold under the name Indian sapphire in international trade. The term is reserved, in modern dealer usage, for Kashmir-origin or for stones described loosely after their colour. In nineteenth-century usage, by contrast, Indian sapphire was a common gemmological label for blue corundum traded through the Indian export houses regardless of underlying source, and old jewellery descriptions invoking the term should be read with that ambiguity in mind.

Verification of origin

Origin determination for sapphire is one of the few cases in which a gemmological laboratory can issue a meaningful provenance opinion. GIA, GRS, SSEF, AGL and Gubelin all offer Kashmir-origin reports, based on a combination of trace-element fingerprinting (gallium, magnesium, iron, titanium ratios), inclusion analysis, ultraviolet-visible spectroscopy and Fourier-transform infrared spectroscopy. A Kashmir attribution from one of these laboratories is the document that supports the substantial premium the market pays.

The premium itself is significant. AGTA market data and major auction-house results have for years shown Kashmir sapphires of fine colour at multiples of comparable Burmese or Sri Lankan stones, with top-grade unheated pieces of three to five carats regularly clearing six figures per carat at Christie's, Sotheby's and Bonhams sales. Heat treatment is uncommon in Kashmir material, and the laboratory-confirmed combination of Kashmir origin and no heat is the highest-value attribution available for blue sapphire.

Buyer cautions

Two cautions are worth noting. First, Kashmir is a frequently misattributed origin: the velvety, slightly milky character that defines the type also appears in some Burmese and Madagascan stones, and a Kashmir attribution should always rest on a contemporary report from one of the senior laboratories rather than on dealer assertion or on an old appraisal. Second, the looser nineteenth-century use of "Indian sapphire" as a colour descriptor has not entirely died out, and a stone offered under this name with no laboratory document and no specific mine attribution is generally a stone of unspecified origin sold under an evocative label.

For the contemporary buyer, the working rule is simple: a Kashmir sapphire is a sapphire with a current report from GIA, GRS, SSEF, AGL or Gubelin attributing it to Kashmir; anything else described as Indian sapphire requires direct enquiry before any premium is paid.