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How to Identify a Precious Stone That Is Polished

For a professional gemologist with access to sophisticated equipment, identification of a polished stone is complicated, but fairly accurate. For the amateur gemologist or the curious jewelry owner, accurate identification is nearly impossible, but you can narrow the possibilities considerably. Two relatively inexpensive items necessary for identification are a jeweler's loupe and a hardness kit. The loop is obtainable at jewelry stores and craft shops. You can purchase a hardness kit online or from a gemology or rock collecting specialty store.

Things You'll Need

Gemstone encyclopedia
Hardness testing kit
Jeweler's loupe

Instructions

- 1
  Purchase a fully illustrated gemstone encyclopedia with colored photographs. To assess the quality of the encyclopedia, look up stones like sapphire and topaz. Both of these stones come in a variety of colors. There are also online resources like the website, All About Gemstones or GemSelect.com, but being able to hold the stone next to a picture may help compare color tones better.
- 2
  Consider the provenance, or history, of the stone. Things like age of the stone (Is it in your great-grandmother's ring?), how much you paid for it and any knowledge of stone treatments (heat, irradiation or filling) will help narrow the possibilities. If you know what the stone should be, you can compare the stone's characteristics to the characteristics listed in the encyclopedia.
- 3
  Identify the color of the stone. This is possibly the most unreliable of identification tools, but it will narrow the possibilities. For example, a red stone is not a sapphire, but a blue stone could be a sapphire, topaz or tourmaline. Clear, colorless stones might be diamonds or white topaz, but diamonds also come in yellow, blue, pink and brown.
- 4
  Test the stone to determine its hardness on the Mohs scale. This scale ranges from 1 to 10 and is measured in whole and half numbers. A sapphire is rated as 9 Mohs, while a topaz is rated 8 Mohs and a tourmaline is between 7 and 7.5 Mohs. Testing for hardness does require scratching the stone, so test in an inconspicuous area or an area that can be easily polished later.
- 5
  Look at the stone in bright sunlight. Some stones, like alexandrite, change color in sunlight versus incandescent or fluorescent light.
- 6
  Examine the stone with a jeweler's loupe. Almost all gemstones have inclusions, or flaws, in the stone. These inclusions range from air bubbles to tiny flecks of mineral or metal. The shape or type of these inclusions will help you to narrow down the possible gemstones.
- 7
  Compare the information you have to your gem stone encyclopedia and make an educated guess.

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