Fine jewelry is jewelry made from real gemstones and fine metals. Costume jewelry is prized more for its design and inventiveness than the materials from which it is made. Costume jewelry can certainly contain gemstones and fine metals but its value is not mostly determined by the materials from which it was made. Think of costume jewelry as “fashion jewelry”.

Below are a few bits of knowledge I’ve picked up over the years to help me identify the materials in jewelry.  Sometimes I obtain a piece of jewelry and am not sure what it is made of.  I’ve gotten pretty good from my years of experience but, if I’m in doubt, I always run to my local jeweler. It took me a while to find a jeweler who was willing to work with me. I pay him for his time, of course, and he knows that I’m not in competition with him. This goes a long way in ensuring his enthusiasm for helping me! His knowledge is invaluable.

Real Pearls vs. Costume Pearls

• Cultured pearls were sometimes put into costume jewelry in the 1960s and earlier. After that date, most costume jewelry will feature plastic or glass pearls. A real pearl will have slight imperfections, bumps, or grit on it if you look at it with a loupe. I use a “tooth test” to tell if a pearl is real.  If you rub a real pearl against your front teeth, you will feel the slight grit. A costume jewelry pearl will feel smooth.  Plastic pearls are lighter in weight than glass pearls and are less desirable.  If you knock a pearl against your teeth and it feels hard but is smooth, it’s a glass pearl. Some high quality simulated pearls will have the same grit as real pearls, so this test is not 100% foolproof.
• The “sun test” is another. Takes your pearls out into the sun. Unless they are very expensive, genuine pearls won’t be perfectly matched under the sun. You will be able to see variations in their appearance if you are holding real pearls.
• Today most pearls are cultured, meaning they were made with the intervention of man.  The only true way to see if a pearl is natural or cultured is from an X-ray. You can probably assume that most jewelry you will see today is made with cultured pearls. If you suspect that you have something finer than a cultured pearl, go and see your jeweler. It will be worth it to you to find out.
• A sign of quality for pearl jewelry will be the setting. Jewelry set into 14K gold or higher is generally of higher quality than 10K or sterling. Today, jewelers may mix materials but this is a good rule of thumb to follow. A nice pearl necklace will be hand-strung with knots in between each pearl. Is the clasp a nice one and does it have a gold stamp on it?
• If you look at your pearls with a loupe and see that the outer coating is coming off, this is a problem. It means you have lower quality cultured pearls which are damaged.

Real Coral vs. Man-Made Coral

• I’ve seen real coral in costume jewelry but I’ve also seen plastic coral and coral made from glass.
• Coral does come in a range of colors from white/cream to deep red.
• Is the coral hard like glass or stone? If not, it’s plastic.
• Get out your loupe. Real branch coral should show imperfections on its surface – tiny pits, bumps. Look at the ends of the coral. In real coral I would expect to see slight roughness, not perfect smoothness. 
• In real coral, I’d expect to see slight variations in color. 
• In branch coral, I’d expect to see variations in each piece. It just cannot all look the same if it is real.

Gemstones vs. Glass

• I am not a jeweler, so when in doubt, I go to see my local jeweler for help. But it helps to remember that “like materials are usually set into like materials”. This means that a fine diamond is probably not going to be set into a low quality setting. As a rule of thumb, I’d look for fine jewelry to be 14K gold or higher.
• Antique and Victorian jewelry did use gemstones in gold filled and gold plated settings.
• Often, translucent gemstones are set into open-back settings so that the light can come from behind and illuminate the gemstone. Turn your jewelry over. Can you see the back of the gemstone? If so, this is an open-backed setting.
• My jeweler always takes his loupe and examines the gemstone for bubbles. If you have a piece of jewelry and are not sure if the stone is real or made of glass, look for tiny bubbles. If you see bubbles, then you can assume you have glass. I do this often for older jewelry that has a large stone in it – Victorian or early 20th century jewelry.
• A gemstone should be set into a piece of jewelry with prongs, not glued in. Glued in stones usually denotes lower quality than prong-set stones.
• For natural semi-precious stones used in costume jewelry, such as agates or quartz, again my rule of thumb is that the real thing should not be perfectly uniform. I would expect to see with my loupe some variations in color, texture, just something to show me it’s not glass.

Hand-Cut Crystal Glass Beads vs. Molded Glass Beads

• Get out the loupe again! Put two identical sized beads side-by-side. Are the facets in exactly the same spots on the beads, exactly the same size, totally identical? If so, then you probably have molded beads. Generally, hand-cut beads denote higher quality than molded beads. In hand-cut beads, you should expect to see slight differences in beads and also slight imperfections. I’m not talking damage but more irregularities in the facets. Also, hand-cut glass sometimes has sharp edges that I would not expect to see in molded glass.

Ivory vs. Bone
Ivory normally has a finer appearance than bone.  It will have fewer marks and striations in the material. Sometimes with bone you can see with the naked eye some cracks, black lines, pits, etc. If you look at ivory with a loupe, it may show a slight grain or cross-hatching in the material on back.

• There is a “hot pin test” for ivory. True ivory is virtually impenetrable with heat and so will not be damaged by this test. Take a needle or a straightened-out safety pin and heat it until it is red-hot. In an unobtrusive spot on the piece, poke it. If the piece is true ivory, there will not be a hole and there will be a tiny mark. Smell the spot. It should smell like burnt protein (burnt hair). Bone is also resistant to heat, but not as much as ivory.  It will not put out the same strong smell as ivory.
• Bone is not free of grain and will ALWAYS have little "pock marks" in it where the marrow or blood was. You may have to use a loupe to see these pock marks. 
• Ivory can yellow over time.