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Frequently Asked Questions (FAQ) / Testing Diamonds with Diamond Testers

Do diamond testing devices really work? Can they tell real from fake diamonds?

Cognac Diamond from GemSelect

Many diamond testers do work, but it's important to understand how they work and what they are testing. Always remember that synthetic diamonds are genuine diamonds and will be identified as such by these simple testers, since their thermal and electrical conductivity values are the same as natural diamond. The original diamond testers performed a thermal conductivity test, and could distinguish genuine diamond from diamond simulants such as cubic zirconia.

However, when the new diamond simulant, moissanite, came on the market, first generation diamond testers could not identify it because its thermal conductivity values are very close to those of diamond. A second generation tester that also tests for electrical conductivity can distinguish moissanite, since moissanite conducts electricty and genuine diamond does not.

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  • First Published: February-20-2006
  • Last Updated: August-16-2017
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    Reproduction (text or graphics) without the express written consent of (SETT Company Ltd.) is strictly prohibited.
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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