Determine Gemstone Authenticity at Home

by Judy Ellis
Question: What are some of the ways I can tell a real gemstone from a CZ or synthetic stone? I would just like a few hints that I can use such as what to look for with a magnifying glass, to tell the difference. Can you give me a few pointers? -Lynne in Sutherlin, Oregon

Oh my goodness, Lynne! Really, there is no sure way to determine between the stone types you list without gemological equipment. One option is to send valuable, questionable stones to the GIA (Gemological Institute of America).

Any good gemstone identification book will tell about a natural gemstone’s properties, including any natural inclusions or flaws (such as feathers, silk, lily pads, etc.) that you can look for by using either a microscope or a 10x loupe.

Of course, there are a few home tests that are not to be counted on, such as:

  • Hold a cut stone to the sun, table toward your eye. if you can see straight through it, it is a form of glass, because glass reflects light, while gem material refracts light.

  • Weigh it: Diamonds weigh more than cubic zirconia.

  • Does it have flaws or inclusions? Lab stones (aka "synthetic") are no different than natural stones, except that lab stones are perfect: they have no flaws or inclusions.

  • The warmth test: If you hold a stone to your upper lip and it stays cold, it is a rock; if it gets warm really quickly, it’s plastic; and if it warms slowly, it’s glass.

One of the least expensive ways to help identify gemstones is to use a combination short and long wave, ultraviolet light, as described in this awesome book: Gem Identification Made Easy, by Antoinette Leonard Matlins. (If the link doesn’t pull up, go to, and search for "Easy gemstone identification tests")

You could also find and join a local Rock and Mineral Club. There you will meet people with all types of knowledge about rocks, gems and fossils, as well as those with lapidary and jewelry making interests. Like me, they are always happy to "talk rocks."

Answer contributed by Dale "Cougar" Armstrong


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  • Category: Stones
  • Technique(s): General Education