Jewelers draw two lines of distinction between types of jewelry. One line separates natural jewelry from lab-created or plated jewelry, while the other divides the former two types from pure costume jewelry which contains no real precious metals or gems. Costume jewelry still serves a purpose, though, as its relatively low price makes it accessible to almost everyone. Jewelry makers can execute beautiful designs in real, lab-created or costume jewelry.
Jewelers count platinum, silver and all shades of gold as precious metals. These metals resist corrosion and are non-reactive, making them ideal for a lifetime of daily wear. Fine jewelry consists of solid platinum or gold either by itself or as a setting for gemstones. Because of its low cost, silver crosses the border between fine jewelry and costume jewelry readily despite its precious appellation. New techniques in metallurgy place titanium and tungsten jewelry in fine jewelry cases as well, and although these metals are not precious, jewelers now use them in fine jewelry.
Plating a base metal with a precious metal results in a less expensive piece of costume jewelry that still has the gleam of real gold or platinum. Electroplating involves passing an electrical current through an electrolyte solution that contains the more desirable metal and using the item that will receive the plating as one of the electrodes in the solution. Metal ions from the electrolyte fluid coat the jewelry and form a thin but permanently bonded layer on the item. An electroplated coating eventually wears away, but until it does, the jewelry looks exactly like precious-metal jewelry for a fraction of the cost.
The least expensive costume jewelry uses metal alloys that superficially resemble gold or platinum, but have none of the precious metals' corrosion resistance. Polished brass can mimic yellow gold, while nickel approximates platinum's shine. These more reactive metals can cause inflammation, itching and skin discolorations for some wearers. A cheap ring can leave a green or black stain on the wearer's hand after prolonged wear. Dipping costume jewelry into clear sealant can keep it from affecting the skin adversely.
Jewelers recognize four precious gems: diamond, ruby, blue sapphire and emerald. Other gemstones fall into the semi-precious category. When people speak of "real" gems, they mean gems that appeared in the wild via natural means. With the exception of pearls, all natural gems are tens to hundreds of millions of years old. Real natural gemstones command the highest prices, especially if they are of good quality. Real precious and semi-precious gems have settings of equally precious metals or of the strong, non-reactive new titanium and tungsten alloys.
Chemically identical to their natural counterparts, lab-created or synthetic gemstones fill the gap between real and fake. They are manufactured versions of real gems and behave in every regard as the natural gems do. They share the same hardness, density and shine. However, their man-made origins make them less valuable than natural stones. Natural rubies and emeralds in particular bear characteristic flaws that set each stone apart from any other; lab-created versions of these precious gems have no flaws, yet cost less because of their artificial perfection.
Imitation gems are not only manufactured, but they also share none of a real or lab-created gem's characteristics aside from color. The cheapest costume gems are molded plastic beads; crafters and costume designers use these sparkling fake gems for more than just jewelry. Faceted crystals, rhinestones and glass are more durable inexpensive imitation gem options. Cubic zirconia, the synthetic crystalline form of zirconium oxide, costs more than other imitation options because its greater hardness makes it appropriate for high-quality costume jewelry.