How to distinguish ruby ​​and garnet

Check rubies for authenticity



Various methods can be used to check rubies for authenticity.

It is easy to test with the Presidium Gem Tester whether it fails with ruby, but it could still be a duplicate.

If you do not have such a device at hand, you can also carry out the following tests.

Exclude grenade. Magnetism is used for this. You take a strong magnet, if the stone reacts to the magnet, it is a garnet and not a ruby.

Endurance test. Ruby has a hardness of 9. If you can scratch glass with the stone, it is ruby ​​or spinel. To recognize a spinel, you take a well-known ruby. If this can scratch the stone, it is a spinel (hardness 8) and not a ruby.

Fluorescence: A ruby ​​glows bright red under short-wave UV light.

Density: Measure the density of the stone with a pycnometer. A ruby ​​has a density of 3.9-4.1, spinel 3.57-3.72, glass 2.50-2.60. The density measurement can also be used to distinguish rubies from ruby ​​doublets, since a doublet has a lower density than a ruby ​​due to the proportion of glass.

Refractometer: Ruby has an RI of 1.757-1.779 and Spinel has an RI of 1.708-1.735.

Birefringence: spinel and garnet are single refractive, ruby ​​birefringent (0.008)

Recognize synthetic rubies. Is rather difficult for the layman. Still, there are a few ways to differentiate syntheses from natural stones.

Extremely clear, beautiful stones and at particularly low prices will usually be syntheses.

Synthetic rubies often show the following signs. Curved stripes, elongated gas bubbles, veil-like inclusions.

In contrast to natural rubies, synthetic rubies allow short-wave UV light to pass through.

Nevertheless, you should always insist on a certificate of authenticity from a recognized laboratory for valuable rubies.