As crystals have grown in popularity, so have the fakes. Some are harmless, like dyed agate slices sold as decor, but others are glass or plastic passed off as natural stone at a natural-stone price. A few simple checks will protect you from most of them.
Simple checks you can do by hand
- Temperature. Real crystals are poor conductors of heat, so they feel cool to the touch and warm up slowly. Glass and plastic reach room temperature quickly and feel warmer straight away. Press a stone to your cheek; genuine quartz stays noticeably cool.
- Bubbles. Hold the piece to the light and look inside. Tiny round air bubbles are a giveaway for glass. Natural crystals may have inclusions, veils or fractures, but not perfectly round bubbles.
- Colour that is too perfect. Vivid, uniform, candy-bright colour is suspicious. Natural stones almost always vary in tone, with cloudy patches and uneven zones. Electric-blue "howlite" and impossibly orange "carnelian" are usually dyed.
- Weight. Real stone is denser than glass or plastic of the same size. A piece that feels surprisingly light for its size is worth questioning.
- Hardness. Quartz-family stones (around 7 on the Mohs scale) will not be scratched by a steel knife and can scratch glass. This test marks the stone, so use it only on an inconspicuous spot, or skip it on tumbled pieces you want to keep pristine.
- Price and source. If a large, flawless amethyst cathedral costs almost nothing, treat it with suspicion. Buy from sellers who can tell you where a stone came from and what it is.
A few names to know
Some materials are manufactured but sold openly. "Cherry quartz", "blue obsidian" and most "opalite" are manufactured glass. "Goldstone" is glass with copper flecks. None of these are crimes if sold honestly. The problem is only when they are sold as something they are not.
Buying with confidence
None of these checks require special tools, and together they catch the great majority of fakes. When a stone passes the cool-touch, no-bubbles and natural-colour tests, you can usually buy with confidence.