Spinel: The Most Undervalued Precious Gemstone

Spinel may be the single most undervalued gemstone in the fine jewelry market. For centuries it was confused with ruby and sapphire — the “Black Prince’s Ruby” set in the British Imperial State Crown is actually a 170ct red spinel. The Timur Ruby, another famous Crown Jewel, is a 352ct red spinel. Spinel was not formally distinguished from corundum as a separate mineral species until the late 18th century, and it has spent the intervening centuries in ruby and sapphire’s shadow. Today, connoisseurs and the trade recognize spinel’s extraordinary qualities — vivid natural color, high dispersion, excellent durability, and near-universal lack of treatment — as the basis for a compelling story and growing demand.

Mineralogy and Properties

Spinel is magnesium aluminum oxide (MgAl2O4), crystallizing in the cubic system. Its wide color range results from trace element substitutions: chromium produces red and pink; iron produces blue, black, and brown; manganese and cobalt contribute to certain blues and pinks. Hardness: 8 on the Mohs scale — very hard, excellent for all jewelry applications. Toughness: excellent. No cleavage. The cubic crystal structure means spinel is singly refractive (isotropic), unlike corundum, which is doubly refractive.

Refractive index: 1.712 to 1.762. Specific gravity: 3.54 to 3.63. Dispersion: 0.020 (similar to sapphire but lower than diamond or demantoid). Spinel can fluoresce red under UV (chromium-bearing red spinels) or show no fluorescence. The combination of high hardness, no cleavage, singly refractive optical behavior, and typically no treatment makes spinel one of the most gemologically straightforward fine stones.

Colors and Varieties

Red Spinel

Red spinel, colored by chromium, is the most historically significant and often the most valuable variety. Fine red spinel from Burma (Mogok) can rival fine ruby in color intensity and is similarly fluorescent — the chromium creates the same kind of glowing, internally lit red quality for which Mogok corundum is famous. The finest specimens, certified as natural and unheated (which virtually all spinels are), command significant prices.

Pink and Magenta Spinel

Hot pink to magenta spinel is one of the most commercially dynamic varieties. Sri Lankan and Burmese pink spinels can show extraordinary saturation — vivid, electric pinks that outperform many pink sapphires at comparable price points. Tanzanian (Mahenge) spinel produces a distinctive, intense red-pink to hot pink that has developed a strong collector following. Mahenge spinels in saturated pink-red tones are among the most coveted in the current market.

Blue Spinel

Blue spinel ranges from grayish-blue (common, less desirable) to vivid cobalt blue (exceptional, very rare). Cobalt-bearing blue spinel from Sri Lanka and Vietnam shows a vivid, saturated blue rivaling fine Kashmir sapphire in color quality, at a fraction of the price. These stones are increasingly recognized by collectors and command growing premiums. The cobalt coloring mechanism is confirmed by spectroscopy.

Lavender and Purple Spinel

Lavender, lilac, and purple spinels from Sri Lanka and Myanmar are beautiful and undervalued. The soft lavender tones of fine Sri Lankan lavender spinel are romantic and distinctive, with no treatment and excellent durability. They represent outstanding value for fashion-forward jewelry.

Black Spinel

Black spinel is optically opaque to near-opaque and has become a fashionable alternative to black diamond and black onyx in contemporary jewelry design. It is durable, takes a high polish, and provides a clean matte-to-glassy black appearance at accessible prices.

Origin and Value

Burma (Mogok and Mandalay)

Burmese spinel — particularly from Mogok — is the benchmark for fine red and pink varieties. Mogok red spinel with strong chromium fluorescence is the closest natural gemstone to the legendary “pigeon blood ruby” appearance, and certified Burmese origin commands premiums in the fine spinel market.

Tanzania (Mahenge, Tunduru)

Mahenge in Tanzania has produced some of the most remarkable hot pink to red spinels seen in the modern market. Tunduru provides a range of commercial spinel. East African production has made fine spinel more available commercially while the finest pieces remain exceptional and premium-priced.

Sri Lanka

Sri Lanka produces the full color range of spinel including the celebrated lavender, cobalt blue, and fine pink. Sri Lankan spinel has been mined for centuries alongside ruby and sapphire.

Treatment: The Untreated Advantage

Virtually all fine spinel is sold without treatment. There is no standard heat treatment protocol for spinel (heating can actually damage it), no filling, no coating used commercially. This is a significant competitive advantage when positioning spinel against treated ruby, heated sapphire, or oiled emerald. The customer can be told honestly: “This stone is exactly as it came from the earth. No heat, no filling, no enhancement. Its color is entirely natural.” That statement, delivered for a vivid hot pink or blue spinel, is enormously compelling.