What’s the Difference Between Mineral Samples and Gem Rough?

For faceting, the distinction between gems and minerals is usually clarity. However, learn why the decision to cut may be an aesthetic or even a moral one.

Home Learning Center Jewelry and Lapidary Questions About Lapidary and Jewelry MakingWhat’s the Difference Between Mineral Samples and Gem Rough?

By International Gem Society

Question:I know the distinction between gems and minerals has a lot to do with human judgment. Gems are typically minerals that we value as beautiful. But what's the difference between "gemstone rough" and "mineral samples?" I've seen many mineral samples for sale that I thought would make beautiful cut gems, but they're worth more as mineral samples. When I'm rock hounding, how can I tell if the crystals I find are facet rough?

gems and minerals - topaz crystals — A cluster of seven gem-quality topaz crystals attached to their feldspar matrix. You could facet these gemstones. But would you? © Rob Lavinsky, www.iRocks.com. Used with permission.

Answer: As far as faceting goes, the most important distinction between gems and minerals is clarity. Most crystals aren't clean. That immediately reduces their value as facet rough.

If you find a crystal with a large clean area, then you get into aesthetics.

Should You Cut It?

Whole crystals are much rarer than broken pieces. If the crystal (or crystals in a cluster) are in good condition, and especially if it has some of the original matrix attached, then you've found a rare prize. It would be a shame (maybe even immoral) to cut specimens of this quality, as there are so few. Great finds like these are worth more whole.

tourmaline mineral sample and gemstone set — The color-zoned tourmaline crystal and gemstonein this "rough and cut" set both came from the same mine. The beautiful crystal contains a colorless "achroite" zone, rare in tourmalines. Pech, Nuristan, Afghanistan, 4.4 x 1.2 x 1.2 cm (crystal), 9.1 cts (gemstone). © Rob Lavinsky, www.iRocks.com. Used with permission.

You'll rarely encounter this situation. Few mineral specimens actually have the clarity needed for faceting. However, gems and minerals don't have to be cut to be appreciated for their beauty.

Donald Clark, CSM IMG

covellite mineral sample — Some minerals, like this covellite crystal on display at the Montana Bureau of Mines and Geology Mineral Museum, are very attractive but too soft to facet. Photo by James St. John. Licensed under CC By 2.0.

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