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Learning the terminology used by sellers of gemstones will help you decide if a particular piece of jewelry is what you’re looking for and if it’s worth the price. 

Find a Reputable Seller

When you start shopping for jewelry, you may be thinking about design, quality, and how much you want to spend. It also pays to do a little homework on the seller. As you search for a jewelry store or online seller:

  • Ask family members, friends, or coworkers for recommendations.
  • Find out what other people say about a seller by typing its name and the words “complaints” or “reviews” into a search engine.
  • Find the store’s refund and return policies — and get them in writing.

Gemstone Basics

There are three main types of gemstones:

  • Natural gemstones are naturally formed crystal or stone. They are classified as precious or semi-precious. Examples include diamonds, rubies, and emeralds.
  • Lab-created gemstones (also called synthetic, laboratory-grown, or manufacturer-created stones) have the same chemical, physical, and visual properties as natural gemstones, but they’re manufactured. They’re often less expensive than natural gemstones — for example moissanite and spinel.
  • Imitation gemstones look like natural stones, but they’re made of other less expensive materials like glass or plastic, and they don’t have the same chemical, physical, and visual properties as natural gemstones. Examples include quartz and cubic zirconia.

The difference between natural and lab-created gems can be hard to detect, so lab-created and imitation gems should be clearly labeled. Ask the seller the origin of the diamond and if they use testing equipment to distinguish between natural and lab-created gems. Don’t assume that because it looks like a natural diamond it is. Moissanite, for example, may look just like a natural, mined diamond, but it is not the same.

Size

A gemstone can be measured by weight, size, or both. The basic unit for weighing a gemstone is the carat — which is different from the “karat” used for gold. A carat gemstone is equal to one-fifth of a gram and is divided into 100 units, called points. For example, a half-carat gemstone weighs 50 points. When a gemstone is measured by its dimensions, the size often is expressed in millimeters — for example, 7x5 millimeters. The weight and dimensions of a gemstone impact its price.

Treatments and enhancements

Treatments or enhancements may improve a gemstone’s appearance or durability, or change its color. The effects of some treatments may lessen or change over time, and treated stones might require special care. Some treatments might affect the value of a stone compared to a similar untreated stone.

Here are some common treatments and their effects:

  • Bleaching lightens and whitens some gemstones, including jade and pearls.
  • Diffusion treatment adds color to the surface of colorless gemstones. The center of the stone remains colorless.
  • Dyeing adds color and improves color uniformity in some gemstones and pearls.
  • Fracture filling hides cracks in gemstones through an injection of colorless plastic or glass to improve the stones’ appearance and durability. This is often used to treat diamonds.
  • Laser drilling removes black inclusions or spots from a diamond. A laser-drilled stone usually doesn’t require special care, but it may not be as valuable as an untreated stone. Jewelers should tell you if a stone was laser-treated.
  • Heating can lighten, darken, or change the color of some gemstones, or improve a stone’s clarity.
  • Impregnating some gemstones with colorless oils, wax, or resins hides a variety of imperfections to improve the stones’ clarity and appearance.
  • Irradiation can add color to colored diamonds, certain other gemstones, and pearls.

Ask if a gemstone has been treated. Sellers should disclose if a treatment is not permanent, creates special care requirements for the gemstone, or if the treatment significantly affects the stone’s value.

Jewelers should also tell you if pearls have been treated in a way that isn’t permanent, creates special care requirements, or significantly affects value.  

Diamonds

When you buy a diamond, some jewelers will give you a grading report from a gemological laboratory. Make sure your sales paperwork includes any details the seller told you, like the gemstone’s origin, weight or size, treatments, and special care requirements. If the seller doesn’t include these details in writing, consider working with someone else.

Diamonds are gemstones evaluated using four criteria:

1. Color often is graded on a scale established by the Gemological Institute of America (GIA). On the GIA scales, color is rated from D to Z, with D at the top. The more color a diamond has, the lower its value.

2. Cut refers to the quality of how the diamond has been shaped, taking into account the diamond’s proportions, polish, and symmetry.

3. Clarity measures the natural imperfections in the stone. On the GIA scales, clarity is rated from flawless to I3. To qualify as “flawless” a diamond must have no visible surface or internal imperfections when viewed under 10-power magnification by a skilled diamond grader.

Some diamonds are treated to improve their appearance. Jewelers might call treatments to improve the appearance of diamonds “clarity enhancements.” These could include fracture filling and lasering, which lessen the value of the stone.  

4. Carat refers to the stone’s weight. The weight may be described in decimal or fractional parts of a carat.

  • If weight is described in decimal parts, the number should be accurate when rounded to the last decimal place. For example, “.30 carat” could represent a diamond that weighs between .295 and .304 carat.
  • If weight is described in fractions, a diamond described as ½ carat could weigh between .47 and .54 carat. If a seller gives a diamond’s weight in fractions, they should tell you the weight is not exact, and tell you the reasonable weight range for the diamond. For example, “The weight range for this diamond is .47 - .54 carats.”

Pearls

Pearls are organic gemstones that can be natural, cultured, or imitation.

  • Natural pearls are made by oysters and other mollusks. Some pearls occur naturally in black, bronze, gold, purple, blue, and orange tints.
  • Cultured pearls also are grown by mollusks, after people put irritants into the shells that cause pearls to grow.
  • Imitation pearls are manufactured with glass, plastic, or other materials.

Natural pearls are very rare, so most jewelry contains cultured or imitation pearls. Cultured pearls are more valuable than imitation pearls. A cultured pearl’s value generally is based on its size, usually stated in millimeters, and the quality of its nacre coating, which gives it luster. Jewelers should tell you if pearls are cultured or imitation.

Report Problems

If you have a problem with a jewelry purchase, try to resolve it with the seller first. If you’re not satisfied, report it to

The Jewelers Vigilance Committee (JVC) has a mediation program that helps some people who have disputes with jewelers. Read more at JVClegal.org/services.

If you have a problem with jewelry bought in person from a company located outside the U.S., report it at econsumer.gov.

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