Spinel is a crystalline precious stone that occurs naturally in a wide range of colours. Its hardness of 8 on the Mohs scale gives it excellent durability. It differs from ruby and sapphire in its chemical composition. Its transparency and brilliance bring it visually close to the most prestigious of those stones.

Spinel and ruby can display very similar red hues, but they differ in chemical composition. Ruby is a variety of corundum coloured by chromium. Spinel is a distinct mineral also coloured by chromium. The two were confused for centuries — the famous "Black Prince" of the British Crown was considered a ruby until 1851. In terms of hardness, ruby scores 9 against 8 for spinel, though spinel remains perfectly suited to daily wear.

The price of a spinel varies considerably depending on colour, weight and origin. Expect to pay €300 to €1,500 per carat for a good-quality stone (1 carat). Mahenge pink spinels from Tanzania reach €3,000 to €10,000 per carat. Burmese "Jedi" red spinels can exceed €15,000 per carat. Cobalt blue spinels remain the rarest and most expensive. At equivalent quality, a spinel typically costs three to five times less than a ruby.

Spinels come primarily from four historic sources. Burma (Mogok) produces the neon-hued "Jedi" red spinels, the most sought-after of all. Tanzania (Mahenge) has been the world reference for fluorescent pink spinels since 2007. Tajikistan (Kuh-i-Lal) yields pink spinels of soft, historically significant tones. Vietnam (Luc Yen) offers spinels in all colours, including rare blues. Sri Lanka rounds out supply with more modest production.

Spinel is one of the very few precious stones that is naturally untreated. More than 95% of spinels on the market receive no heat treatment or chemical enhancement whatsoever. This is one of its greatest advantages over ruby and sapphire, and it holds particular appeal for collectors and connoisseurs. Bonnot Paris guarantees the absence of treatment for every spinel in the collection, confirmed systematically by an independent certificate.

Yes, spinel is an excellent choice for an engagement ring. Its hardness of 8 on the Mohs scale ensures it holds up beautifully over time, withstanding daily wear without requiring a protective setting. Its natural rarity and untreated character make it a genuinely meaningful choice. Spinel offers an original alternative to the classic sapphire or ruby, and its wide colour palette makes it possible to find a truly unique stone.

Mahenge spinel refers to the fluorescent pink spinels discovered at the eponymous deposit in Tanzania. The landmark find dates to August 2007, when an exceptional 52 kg crystal was unearthed — a discovery that transformed the spinel market. The Mahenge colour is defined by a unique neon fluorescent pink, resulting from a rare combination of chromium and an absence of iron. Mahenge spinels reach €3,000 to €15,000 per carat depending on quality.