Spinel one of the most colorfull gems of the world. The history says spinel is a valuable gem since long. Looking at Urdu,Persian poetry we find this gem to highlight the resemblance for beuty its Called Laal (لعل) its also a a very comon muslim name.
A famous myth about spinel is that it glows in the dark. Reffering to a famous tale (لعل بھی مل جائیں اور لالی بھی نہ جائے) in the areas of Phnjab and sindh(Pakistan).
Spinel comes in variety of colours like red,blue,purple,etc. Spinel has bright viterous luster and got quite good hardness of 8. Which makes it durable against scratches.
The chemical formula of this mineral is MgAl2O4.
The specific graviety is 3.60 and Refractive index is 1.71 to 1.72
It gets its red color with the same coloring element which is responsible for coloring of Ruby. That is CHROMIUM(Cr). Blue spinel also exist in nature and it’s color is because of Iron(Fe) mostly. Another variety of blue color spinel is also present in nature with Cobalt(Co) as a coloring element. Which changes to red under Chelsea color filter.
Purple color is found because of the mixing of red and blue with both impurities of CHROMIUM AND IRON.
Red spinel can be easily confused with ruby. But you can be differentiate easily with the help of DI-CHROSCOPE and Polariscope.
Burma is a very famous source of spinles but with the smaller size
Sri Lanka also contribute spinels to international market. Moreover Pakistan is the the country enriched with biger crystals of spinels which are located in the Himalayan mountains located in huza valley.
Gem pockets of these mountains contain red,blue,purple spinels and most interesting part is the cobalt blue spinel which is very rare and too gemy.
Spinels have the same inclusions as of corondum. Which include zircon helos,boehmite needles,crystals of spinels itself and rutile needles etc
Treatments And synthatics
No treatments to spinels 😀 thank God. Synthatic spinel are mostly cross hatch and their R.I is 1.73