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Spinel, composition magnesium aluminium oxide, occurs in the same deposits and exhibits the same hues as the aluminium oxide gems ruby and sapphire so that for centuries it was confused with them. 

This was the case with the fine 170ct cabochon cut red spinel set above the Cullinan II in the Imperial State Crown of England. This is a stone with a long and chequered history. It was first recorded in the mid-fourteenth century as belonging to Abu Said, the Moorish Prince of Granada.

When the Moorish Kingdom came under attack during the Christian re-conquest of Iberia (see the movie El Cid) Abu Said went to offer his surrender to the Castilian ruler, Don Pedro the Cruel.

However Don Pedro did not honour the truce and he ordered that Said’s retinue should be put to death. Then, legend has it, the Don stabbed Said himself and on searching his clothing found the great “ruby” that he added to his collection.

Don Pedro’s illegitimate brother Henry led a revolt against him in 1366. Lacking sufficient forces the Don was obliged to enlist the aid of Edward, the Black Prince of England to help him put down the revolt. Having achieved a successful outcome the prince demanded that the Don give him the “ruby” in exchange for services rendered. In the light of subsequent events it can be assumed that Edward must have taken the stone with him when he returned to England.


The stone does not come to light again until 1415 when it is recorded that Henry V wore it in a gem-encrusted helmet when he won a remarkable victory over a numerically vastly superior French force at the Battle of Agincourt.

Richard III is reputed to have worn it in his helmet, with less success, at the Battle of Bosworth. An event that ended the reign of the Plantagenets and brought the Tudors to the throne.

The stone is also mentioned in the inventory of 1521 that was ordered by the Tudor King Henry VIII.    

A new Imperial State Crown was made for the coronation of Queen Victoria in 1838. It featured the Black Prince’s “ruby” at the front. The lighter crown that was made in 1937 included the cushion-shaped 317.4ct Cullinan II diamond. The ruby-red cabochon mounted above it was now known to be a red spinel.

Other notable stones include the Samarian, a red spinel of 500cts, believed to be the world’s largest and held in the Iranian Crown Jewels. The Russian Imperial Crown contains an irregular pear shaped red spinel of 392.78cts. The Crown Jewels of England include a 352.5ct irregular red spinel known as the “Timur Ruby”.

Ruby red and cobalt blue are the most popular colours in spinel. Other colours such as rose pink, purple, lavender, violet-blue, royal blue, navy blue, greenish-blue, mauve, yellow, orange and brown can be attractive and usually more affordable.

Spinel crystallises in the cubic system and it generally forms octahedra. The points of this form are probably responsible for its name that is derived from the Latin word spina or thorn.

With a hardness of eight and no cleavage it is a hard wearing gem and suitable for any jewellery application. Spinel is not usually treated or enhanced. The unrealistic colouring and the difference in refractive index make it is easy to distinguish between natural spinel and the artificial material that is marketed as synthetic spinel.


Fellow, Gem-A(GtBr)  /  Graduate gemologist GIA (USA)  /  Certified Evaluator (SA)
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