Most common: red, pink, orange, blue, violet, purple
Others are: brown, black
Rarely: yellow and colorless
Color change: greysh blue in daylight to purple in incandescent light
Clarity
Due to the octahedral nature of spinel rough, the most common shape seen is the cushion
Rounds are also seen, as are other shapes, such as the emerald cut
(click on colour to find other gemstones and jewelry)
TREATMENTS
CUT
Spinels are rarely treated, though occasional experimental heating of spinel has been reported
Spinels with surface reaching fissures are infrequently treated with oils or polymers
Care
It is preferable to simply use a damp soft cloth or a soft bristle toothbrush to clean the gemstones and spinel jewellery.
Colour, carat weight, clarity and origin all play a role in how spinels are valued and collected. Gems whose provenance can be ascertained always have collectors. Red spinels that are deep red, large and relatively free of inclusions are also highly desired. So too are rare, deep blue spinels, particularly when a gemological laboratory has determined that cobalt is the colouring agent. Locality is playing an important role for collectors as well. Rare spinels from the Pamir Mountains are collectible, as are spinels from Burma. New localities that produce desirable colour - anywhere from pink to deep red are collectible.
collect
In terms of clarity, spinel is often cleaner than ruby
The very finest reds are so rare that some clarity defect is almost always present (usually fractures)
Included crystals are quite common in spinel. Many stones display natural iron-oxide stains in their fractures
Famous and Influential English Jeweler Edwin Streeter on Sapphires. He led a consortium against Baron Rodthschild for the rights of the Burma Ruby mines.
More on Sapphire. We will add some more themes pertaining to sapphires here. Please bear with us as this is a labour of love, and very very time consuming.
Modern Jeweler has an excellent 4-page review article on Padparadscha Sapphire.
Pala Gems has an amazing article written by Dick Hughes on what constitutes a Sapphire what a Ruby and how colors can confuse you.
A review article of the life of gemologist Robert Crowningshield , the one who wrote the famous 1983 Gem and Gemology Article about Padparadscha Sapphire, and later the 1989 article on the Hope Diamond.