Spinel: August's Hidden-Gem Birthstone
Spinel was added to the modern August birthstone list in 2016 as a third option alongside peridot and sardonyx. Long mistaken for ruby (the famous Black Prince's Ruby in the American Crown Jewels is actually a red spinel), spinel has emerged in the last decade as a serious collector gemstone with rich color range and strong durability. This guide covers what spinel is, the main varieties, and what to look for when buying one.
In short: Spinel was added to August birthstones in 2016 (alongside peridot and sardonyx) and is finally getting the recognition it deserves. Mohs 8, no cleavage plane, typically untreated — making it more durable than topaz and more reliable than commonly-treated coloured gemstones. Available in red, pink, blue, and purple, often priced 30-60% below ruby or sapphire of equivalent colour. The famous "Black Prince's Ruby" in the British Crown Jewels is actually a spinel.
What is spinel
Spinel is a magnesium aluminium oxide that crystallises in cubic form. It scores 8 on the Mohs hardness scale — durable enough for daily-wear jewelry, with no cleavage plane (unlike topaz, which can split). Pure spinel is colourless; trace elements produce red, pink, blue, purple, orange, and rarely the prized "cobalt blue" color. Most spinel is naturally colored and not treated — a significant advantage over corundum varieties that are commonly heat-treated.
Spinel varieties
Red spinel is the historically most-valuable variety — vivid pigeon-blood reds command prices approaching fine ruby. Pink spinel (Mahenge pink from Tanzania is particularly prized) has soared in popularity over the past decade and offers a clean alternative to pink sapphire. Cobalt blue spinel from Sri Lanka and Vietnam shows neon-vivid color found in almost no other gemstone. Purple, orange, and grey-blue spinels offer collector character at lower prices.
Origin and supply
Burma (Myanmar) historically produced the finest red spinels, including the famous Mogok specimens. Tanzania's Mahenge mine, discovered in 2007, produces extraordinary vivid pink spinels in larger sizes than any prior source. Vietnam, Sri Lanka, Tajikistan, and Pakistan all produce significant spinel. Unlike many colored gemstones, spinel supply remains active and growing — though top-quality stones in larger sizes are scarce and command rising prices.
