How to Tell a Real Gemstone From Glass

Glass is the oldest gemstone imitation there is. It’s cheap, it can be any color, and in a dim photo it can look a lot like the real thing.

Here’s how to tell the difference, mostly without special equipment.

1. Look for bubbles

Get a 10x jeweler’s loupe. They’re inexpensive and worth owning. Look inside the stone.

• Glass often has round gas bubbles and swirly flow lines, from being melted and poured.
• Natural stones have inclusions that look different: tiny crystals, needles, feathery cracks, cloudy patches.

Round bubbles are a strong sign of glass. Natural stones almost never have them.

2. Check the edges and surface

Glass is softer than most gems, around 5.5 on the hardness scale. Over time it gets scratched and chipped easily.

• Worn, rounded facet edges on a piece that’s barely been worn are a warning sign.
• Mold marks or a slightly rounded, “melted” look on facets suggest pressed glass.

3. The temperature test

Hold the stone against your lip or cheek. Many natural gemstones, like quartz and topaz, feel cool and stay cool a little longer. Glass tends to warm up faster.

It’s not a perfect test, but if something feels warm and plasticky right away, be suspicious.

4. Too perfect is suspicious

Natural stones vary. Color zones, slight cloudiness, a tiny inclusion near the edge. A large, flawless, perfectly even stone at a low price is more likely to be glass, or lab-made.

5. Look at the price

A big “natural ruby” in a $20 ring isn’t one. A real ammolite, aquamarine or fire opal costs real money before anyone even sets it. If the price seems impossible, it probably is.

6. Read the words carefully

Sellers sometimes use words that sound like gemstones but aren’t:

• “Crystal” in jewelry usually means glass, often leaded glass. That includes famous crystal brands.
• “Simulated” means it imitates a gem. It could be glass or plastic.
• “Created” or “lab-grown” means made in a lab. Real material, not mined.
• Made-up trade names like “Mexican jade” or “Malaysia jade,” and other names that pair a place with a gem are a reason to ask questions.
• “Genuine” or “natural” should mean mined from the earth. Ask anyway.

7. Ask the seller

A good seller can tell you what the stone is, whether it’s natural, and whether it’s been treated. If they can’t or won’t answer, that’s your answer.

For an expensive purchase, ask for a report from an independent gem lab.

What not to do

Don’t scratch-test it. Scratching a stone to test it can ruin a real gem. It’s not worth it.

My promise

Every stone in my shop is natural. I choose each one myself, and if a stone has been treated or is part of a doublet or triplet, I’ll tell you. If I’m ever unsure, I’ll say so.

If you want to understand the difference between natural and lab-made, read why I only use natural stones. Or browse my one-of-a-kind gemstone jewelry.

Have you ever bought a “gemstone” that turned out to be glass? Tell me the story.