Introduction
Spinel, a gemstone long overshadowed by sapphires and rubies, is finally getting the recognition it deserves in the world of fine jewellery. With its captivating array of colours, exceptional durability, and fascinating history, spinel is becoming a favourite among collectors and jewellery enthusiasts alike. But what makes this gemstone so special? Let’s dive into its chemical composition, history, properties, and why you should consider adding it to your collection.
Chemical Composition
Spinel is composed of magnesium aluminium oxide (MgAl2O4) and crystallizes in the cubic system. This structure gives spinel its remarkable clarity and vibrant colours. Trace elements like chromium, iron, and cobalt influence its colour palette, which ranges from vivid reds to blues, purples, pinks, and even black.
Derivation of the Name
The name 'spinel' is thought to derive from the Latin word spina, meaning 'thorn', due to its pointed crystal formations. Alternatively, it might come from the Greek spinther, meaning 'spark', a nod to the gemstone's dazzling brilliance.
Similarity to Sapphire
Spinel is often confused with sapphire due to its similar appearance, especially in blue hues. Historically, many famous sapphires turned out to be spinel’s. Both belong to different mineral families—sapphires are corundum (aluminium oxide) while spinel’s are magnesium aluminium oxide. The difference is subtle but significant.
Colours and Variety
Spinels come in virtually every colour. Reds rival rubies, blues echo sapphires, and pinks are as delicate as morganites. The presence of chromium gives red spinel its vibrancy, while iron imparts darker tones. The image on the right shows blue spinel crystals in a marble matrix (photo credit Geminlogical).
Durability and Suitability for Jewellery
Spinel ranks 7.5 to 8 on the Mohs hardness scale, making it durable enough for everyday wear. Its resistance to scratching, combined with high lustre and clarity, makes it an excellent choice for rings, necklaces, earrings, and bracelets.
Geographical Sources
Spinel is found worldwide, with notable sources including:
Myanmar (Burma) – known for vivid red spinels.
Sri Lanka – yields a rainbow of colours.
Tajikistan – famous for pinkish-red hues.
Vietnam – produces mesmerizing cobalt-blue spinels.
Tanzania – known for vibrant pinks and purples.
Crystal Shapes and Forms
Spinel crystals commonly form as octahedrons—eight-sided structures that resemble two pyramids joined at their bases. This natural geometry contributes to the gemstone’s natural sparkle. The image on the right shows a spinel crystal exhibiting the classic octahedral shape. The image below shows more of a cluster of crystals together but the triangle shape is still visible. Both are from Vietnam.
Why Spinel Was Confused with Sapphires and Rubies
Before modern gemmological techniques, gemstones were identified by colour alone. Red spinels were considered rubies, while blue ones were assumed to be sapphires. The distinction wasn’t clarified until the 18th century, explaining why historical records frequently mention 'rubies' that were, in fact, spinels.
Distinguishing Spinel from Sapphire
Gemmologists use advanced tools to differentiate spinels from sapphires. Key distinctions include:
Refractive Index (RI): Spinel has a single RI (~1.71) compared to sapphire’s double RI (~1.76-1.78).
Pleochroism: Spinel lacks pleochroism, while sapphires often show two colours when viewed from different angles.
Hardness Test: Spinel is slightly softer than sapphire.
That said, I am a gemmologist and it is not easy to identify a spinel from visual appearance alone. It is not uncommon to find spinels and sapphires mixed up in parcels of gemstones.
Historical and Cultural Significance
Spinel has adorned royal collections for centuries. The most famous example is the "Black Prince's Ruby" in the British Imperial State Crown. This striking red gem, set above the Cullinan II diamond, was believed to be a ruby for centuries until it was identified as spinel.
Global Popularity
United States: Spinels are increasingly popular among millennials seeking colourful, unique engagement rings. Typically the US market is much bolder than the UK when it comes to colourful jewellery.
China: Chinese consumers are incredibly savvy and collectors are paying exceptionally high prices for large stones with great colour and clarity. Certainly when I was at the gem market in Sri Lanka the Chinese buyers were snapping up all the large spinels.
Folklore and Metaphysical Properties
Spinel is believed to inspire passion, devotion, and longevity. Ancient warriors wore red spinels for protection in battle, while today, it's associated with revitalizing energy and fostering creativity.
The UK Market: An Underrated Treasure
Despite its royal connections, spinel remains underappreciated in the UK. However, discerning collectors are quietly acquiring these gems, recognising their rarity and historical significance. With rising demand globally, especially in Asia and the US, the time to invest in spinel is now.
Conclusion: Don’t Miss Out!
Spinel, with its vibrant colours, rich history, and durability, is an unsung hero of the gemstone world. Whether you're a collector, jeweller, or simply someone who loves beautiful gems, spinel offers unparalleled beauty and heritage. When compared to sapphires, they are indistinguishable to most people and spinels are much much more affordable - for now. Don’t wait until the rest of the world catches on—make spinel part of your collection today!