Often mistaken as Rubies, Spinel are actually on many royal jewellery, famously on England’s Imperial State Crown and The Timur Ruby. It is the treasured property of emperors and kings, often passing through many hands as spoils of war. Increased demand for ruby alternatives rekindled appreciation the gem’s rich colour.
Chemistry: Magnesium Aluminum Oxide (MgAl2O4)
Refractive Index: 1.71 – 1.73
Specific Gravity:3.54 – 3.63
Treatments / Enhancements
Heat Treatment is usually used to improve colour and clarity
Sri lanka, Myanmar, Vietnam, Madagascar, Tanzania
Colour is the most significant factor affecting the value of a spinel.
Colour preferences do change in time and from culture to culture. Nevertheless, the most sought after colour is intense red and cobalt blue. Spinel also come in a variety of colours as well, ranging from vibrant hot pink to vivid orange tones to lighter toned pastel hues of violet blue and purple. The lighter tones are usually not as attractive as compared to the more vivid ones thus theres less demand for it, resulting to lower prices.
Spinels with different undertones
Colour Grades of Spinels
Spinels not only have different colour/undertone shades, they also come shades of blue and violet with varying intensity as well. Below is some of the Tanzanites with different shade intensity.
Colours of the Spinel
With large range of colour hues, there has to be a ways to differentiate between the shades. Different shades of Spinel will result in different prices for the gem.
For Red Spinels, their hues often range around orangey red to purplish red. Pure red or slightly purplish red spinels with medium to medium-dark tones are considered to be of the highest quality. A top quality 5 carat spinel may only sell for a tenth of the price of a ruby with same qualities while a pink spinel sells less than a pink sapphire.
Blue Spinels have their hues range from violet blue to very slightly greenish blue. Most blue spinels contain greyish looks due to the low saturation. The most valued are the ones with intense violet blue or pure blue hues that rivals blue sapphires.
Clarity of a gem is judged based off the gem’s opacity and how much inclusions does the gem contain. The assessment of clarity is often done thru eye clean and it follow the same grading as with diamonds. Inclusions within the gem affects the value of the gem. The more visible the inclusions are to the visible eye, the lower the value of the gem.
Spinels sold for jewelry has inclusions that can only be seen under magnification. Any eye visible inclusions decreases the gems value. Inclusions that might pose durability problems as well, causing fractures and lowering spinel’s value significantly.
Clarity Grades of Spinels
Clarity in transparent spinel is assessed by naked eye only and at distance of about 40cm. Spinels are classified as type 2 stones. This means that there are eye clean, meaning that theres usually no visible inclusions within the gem.
Some inclusion within Spinel can raise its value instead of decreasing it. Spinels sometimes contain inclusions that highly resembles fingerprints. It is very unique that it causes the value of the gem to increase.
The shape of the spinel crystal influences the finished stone’s shape and size. However due spinel’s scarcity within the market, it is cut in non conventional sizes in order to save weight and maximise the amount of gems available. Gem cutters have to consider the tanzanite rough’s depth of colour, durability, and inclusions when making cutting decisions. This is to minimise the weight loss from the cutting as it will affect the value of the final gem.
Gemstones such as spinel are denser than diamonds, therefore the carat weight for a gemstones differs from that of a diamond. Size of gemstones, including spinel, are measured by carat as well as their diameter in millimetres. However, Spinels are more valued for their colour, cut and clarity.
Spinels that are considerably large have a high price per carat. Finest Spinels with the deepest colour of red, pink and blue over 5 carats are the rarest and highest in price. The larger the size, the lower the availability, the more expensive the gemstone.