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How to Tell Topaz From Sapphire Stones

by Yvonne Hawkins

Overview

Although some gemstones are more identifiable than others, topaz and sapphire share many physical characteristics that make them difficult for the untrained eye to tell apart. Their similarities in color varieties, hardness and luster are comparable, but there are also individual qualities of each stone that distinguish them from one another. With a few observations and tests, it's possible to tell the difference between the two.

Color variations of topaz

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Identification

Step 1

Examine the color of the stone. Topaz varieties occur most commonly in golden brown to yellow tones but also in orange, red, blue, green and pink. The most popular sapphire variety is the blue sapphire, but it can occur in almost any color (except red, which is classified as a ruby.)

Blue sapphire ring

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Step 2

Observe the lustre, or shine, of the gemstone. Sapphires can have a slightly higher lustre as the result of a higher refractive index, but because the two are so similar it would be best to use a refractometer to measure these qualities. A refractometer measures the amount of light that is bent when passing through a material. A topaz has a refractive index of approximately 1.61-1.64, while a sapphire measures around 1.76-1.78.
Step 3

Test the hardness of the stone. There are testing kits that examine the hardness of the stone on the Mohs scale, which is used by gemologists. The scale ranges from 1 (talc) to 10 (diamond). A topaz ranks at an 8 on the Mohs, while sapphire is a 9. The kit will usually come with different specimens or minerals that are used to scratch the gemstone, which will allow you to identify where the gemstone lies on the hardness scale.
Step 4

Consult a professional jeweler or gemologist. If you're still in doubt after these tests and observations, find a reliable and qualified professional to examine your stone. There can be a great difference in value between topaz and sapphire gemstones, so it's important to find out before you consider buying or selling.

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Topaz or sapphire stone Refractometer Hardness testing kit
Topaz or sapphire stone
Refractometer
Hardness testing kit
Be sure to get references and recommendations before consulting a professional. Some jewelers aren't necessarily qualified or trained to identify gemstones and could try to sell you a stone of lesser quality.
Be sure to get references and recommendations before consulting a professional. Some jewelers aren't necessarily qualified or trained to identify gemstones and could try to sell you a stone of lesser quality.