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 place it visually alongside the most prestigious coloured stones.

Spinel and ruby can share strikingly similar red hues, but they differ in chemical composition. Ruby belongs to the corundum family and owes its colour to chromium. Spinel is a distinct mineral, also coloured by chromium, yet separate in structure. The two were confused for centuries — the famous 'Black Prince's Ruby' in the British Crown Jewels was identified as a spinel only in 1851. In terms of hardness, ruby scores 9 on the Mohs scale against 8 for spinel. Spinel nonetheless remains perfectly suited to everyday 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 spinel of around 1 carat. Mahenge pink spinels from Tanzania reach €3,000 to €10,000 per carat. 'Jedi' red spinels from Burma can exceed €15,000 per carat. Cobalt blue spinels remain the rarest and most expensive of all. At equivalent quality, a spinel generally 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 on the market. Tanzania (Mahenge) has been the world reference for fluorescent pink spinels since 2007. Tajikistan (Kuh-i-Lal) yields spinels in soft, historically significant pink tones. Vietnam (Luc Yen) offers spinels across a broad colour range, including rare blues. Sri Lanka rounds out the 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 or sapphire, and a quality that particularly appeals to connoisseurs and collectors. Bonnot Paris guarantees the untreated status of every spinel in the collection, systematically confirmed by an independent certificate.

Yes, spinel is an excellent choice for an engagement ring. Its hardness of 8 on the Mohs scale ensures outstanding durability over time. It withstands everyday wear without requiring a protective setting. Its natural rarity and untreated status make it a genuinely meaningful choice. Spinel offers a distinctive alternative to the classic sapphire or ruby. Its wide colour range means there is always a truly unique stone to be found.

Mahenge spinel refers to the fluorescent pink spinels discovered at the deposit of the same name in Tanzania. The defining moment came in August 2007, with the discovery of an exceptional 52 kg crystal. This find transformed the spinel market entirely. Mahenge colour is characterised by a unique neon fluorescent pink, resulting from a rare combination of chromium and an absence of iron. Mahenge spinels command €3,000 to €15,000 per carat depending on quality.