I have what I believe to be a very large Star Spinel that I bought in Afghanistan, when I shine a bright (60 lumens) flashlight into it I feel it burning my finger like a magnifying glass. Has anyone ever heard of this happening before. The stone is set in a large mans ring about size 12 and has a silver band with peacocks on the sides. It has a cabochon dome shape with a flat bottom stone.
This type of gem is made of a group of minerals composed principally of oxides of magnesium, aluminum, iron, manganese, chromium, etc., and you pass 60 lumen it cant cope with such hard flash. but its not a matter of worry. It is one of the good quality stone. People in Afghanistan uses it as their Engagement Ring gem.