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: Unheated Sapphire Gems
Frequently Asked Questions (FAQ) / Heat Treated

How do I determine that a sapphire has not been heated?

Determining conclusively that a sapphire has not been heat-treated is something that only a very experienced gemologist can do. Gemologists examine internal structures under high magnification and look for the presence of crystal structures that would be altered by heat treatment, since many characteristic inclusions such as rutile and zircon crystals have a lower melting point than corundum. Some laboratories also use high-tech tools such as Raman spectroscopy and laser tomography.

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  • First Published: February-20-2006
  • Last Updated: November-11-2014
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Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart