Colour Changing Cobalt Spinel
Spinel derives its name from the Latin word “Spina” for thorn, referring to the pointed tip and octahedral crystalline form of the stone. Before the Middle Ages when there was limited knowledge and resources of gemology it had been mistaken as a member of the corundum family. The qualities of spinels – such as rich intense colour, hardness and glitter – misled many to consider them rubies. Many famous rubies in history, in fact, turned out to be spinels. These include the 170-carat Black Prince Ruby, set atop the Imperial State Crown of the British Royal Family, the 350-carat Timur Ruby owned by Queen Elizabeth II and also the “rubies” mounted on the head-dresses of senior court officials in Qing Dynasty of China.
According to the book Geographic Origin Determination of Coloured Gemstones, “premiumquality spinel was historically misinterpreted as ruby, which led to the undervaluation of spinel in the gemstone market for a long time. In fact, spinel is less abundant than ruby. The probability of finding a ruby is 200 times more than finding a spinal.” Now that the misunderstandings are clarified, spinel has been restored to its original glory, as its market value continues to rebound steadily.
Besides red, spinel also comes in other colours, including blue, which is long cherished by Jewellery collectors. While iron spinel and zinc spinel are bluish too, none of them surpass cobalt spinel in value. Characterized by its rarity, cobalt spinel is considered extraordinary for the brilliant radiance it evokes that is hardly seen in other gems. Amongst cobalt spinels, only the rarest possesses the colour-changing characteristics, due to the conditions of light source and ions in these stones. Colour-changing spinel appears blue in daylight but turns purplish under incandescent light, looking enchanting in different ways.
This autumn, Tiancheng International is pleased to present a colour-changing cobalt spinel of 25.79 carats from Sri Lanka (Lot 144). Mistaken for a blue sapphire, it had been stored in a private fault for over 50 years until the rediscovery of its original value by our specialists. By far the largest colour changing cobalt spinel to be offered at auction, the lot has astounded experienced gemstone dealers by its tremendous size. Endowed with extraordinary colour-changing characteristics, this cobalt spinel has a strong investment value and is considered a rare treasure to discerning collectors.