Kornerupine and Sinhalite: Rare Gems of Sri Lanka and Beyond

Among the rarest facetable gemstones known, kornerupine and sinhalite occupy a special place in the collector’s pantheon—beautiful, durable, and so scarce that most jewelry professionals will never handle a fine example. Yet their rarity is precisely their appeal to specialist collectors. This guide introduces both gems with the depth that informed professionals need.

Kornerupine

Kornerupine is a complex boron-magnesium-aluminum silicate mineral named for Danish geologist Andreas Nikolaus Kornerup. It forms in metamorphic and pegmatitic environments and has been found in Myanmar, Sri Lanka, Kenya, Tanzania, Greenland, Canada, and Madagascar. The gem is strongly trichroic—most commonly appearing greenish to brownish in different crystal directions, though rare pink and colorless varieties exist.

Kornerupine Properties

Color: Typically bottle green to yellowish-green; rare pink, brown, and colorless also known

Hardness: Mohs 6.5–7; durable enough for jewelry

Luster: Vitreous; good brilliance when well-cut

Pleochroism: Strong; cutters must orient the stone carefully to maximize color

Chatoyancy: Some kornerupine shows a strong cat’s eye—among the most prized varieties

Size: Most faceted stones are small (under 2 carats); larger stones are exceptional

Kornerupine Cat’s Eye

Cat’s eye kornerupine—produced by parallel needle inclusions—is one of the most sought collector gems. The eye is typically sharp and well-defined, appearing on a green to brown cabochon. Fine cat’s eye kornerupine above 3 carats is rare enough to be considered a museum-quality gem.

Sinhalite

Sinhalite was identified as a distinct mineral species in 1952—previously it had been mistaken for peridot or brown tourmaline. Named for Sinhala, the Sanskrit name for Sri Lanka (its primary source), sinhalite is a magnesium aluminum borate that forms in contact metamorphic environments. Most sinhalite occurs in alluvial gem gravels in Sri Lanka, with minor occurrences in Myanmar and Tanzania.

Sinhalite Properties

Color: Pale yellowish-brown to dark greenish-brown; the classic warm honey-brown is most distinctive

Hardness: Mohs 6.5–7; adequate for jewelry

Luster: Vitreous to resinous; stones have a warm, glowing quality under light

Pleochroism: Moderate; shows pale yellow, yellow-brown, and dark brown in different directions

Clarity: Typically eye-clean; inclusions are not common in faceted material

Size: Most stones are under 3 carats; larger examples are very rare

Distinguishing Sinhalite from Similar Gems

Sinhalite’s brown color and moderate refractive index can lead to confusion with peridot (typically greener), hessonite garnet (typically more orange), and brown tourmaline (higher RI). Specific gravity testing (sinhalite: 3.47–3.50) and spectroscopic analysis provide definitive identification. Gemological laboratory confirmation is recommended for any sinhalite sold as a collector or investment gem.