Is faceted glass, cut and usually foil backed to throw light straight back at you.
Also called: rhinestone, glass crystal
Measurement
Mohs 5 to 6
The basics
What to know about crystal
Crystal in jewelry means glass made deliberately for sparkle. The historic recipe added lead oxide, up to about a third by weight. That raised the refractive index and made the glass heavier and brighter. Many makers now use barium or zinc formulas that reach a similar effect without lead. At Mohs 5 to 6 it is softer than the quartz in ordinary dust, so wiping it with a dry cloth slowly scratches the surface.
Most stones are machine faceted and then given a thin metallic foil on the back. The foil acts as a mirror and returns light that would otherwise pass straight through. That foil, and the glue holding the stone in its cup, are the weak points. Water creeps behind the backing and the stone turns gray or cloudy, and it also softens the adhesive until stones start dropping out. No ultrasonic cleaner, no washing up, no swimming.
Coatings extend the range further. The rainbow shimmer sold as aurora borealis is a vapor deposited layer on the surface, and it scratches off with wear like any coating. Judged honestly, crystal delivers more sparkle per dollar than anything else and comes in colors no gemstone can match, with a life measured in occasions rather than years. Store pieces flat in a dry box and wipe them only with a barely damp cloth.
In photos
Crystal on real products
See this option on different products. Open a photo for a larger view, or select the name to read its guide.
Crystal stones start as a glass batch. Silica sand is melted with fluxes and with additives chosen to raise the refractive index. Traditionally that meant lead oxide, and now it is often barium or zinc. The molten glass is pressed or drawn into blanks, annealed to relieve internal stress, then faceted by machine against abrasive wheels. Machine faceting is what allows identical stones by the thousand.
Backs are coated in a vacuum chamber, where a thin metallic film is deposited to act as a mirror. Surface effects such as the aurora borealis finish are applied the same way. Finished stones are either glued into cup settings, held by prongs, or set into channels. Pointed back stones sit in metal cups, while flat backs are glued directly to a surface. That glued construction is the one most likely to shed stones over time.
Best for
When it works well
Occasion and costume pieces use crystal because the sparkle carries under stage and party lighting.
Color matching an outfit is possible in a way gemstones cannot manage, since glass takes any hue.
Large scale designs stay affordable and light, which matters for headpieces and heavy collars.
Buying for a single event gets maximum effect for the smallest outlay.
