1. Observation: Natural crystals often contain impurities due to environmental influences during their formation. When observed against the sun, faint, even, fine horizontal lines or wispy, cloud-like inclusions can be seen. Fake crystals, often made from melted scraps of inferior crystal or glass, polished, and colored, lack these uniform lines and cloud-like inclusions.
2. Tongue Test: Even in the sweltering heat of summer, licking the surface of a natural crystal will produce a cool, refreshing sensation. Fake crystals will not provide this cooling sensation.
3. Light Test: When placed upright in sunlight, a natural crystal will emit beautiful light from any angle. Fake crystals will not.
4. Hardness Test: Natural crystals are hard. Gently scratching the surface with a small stone will not leave a mark; if a scratch is left, it is a fake crystal.
5. Polarizing Microscope Test: Under a polarizing microscope, rotating the crystal 360 degrees will show four bright and four dark changes; a fake crystal will not show this change.
6. Dichroism test: Natural amethyst exhibits dichroism, while fake amethyst does not.
7. Magnifying glass test: Examine the amethyst under transmitted light with a 10x magnifying glass. If air bubbles are found, it's almost certainly a fake.
8. Hair test: Place the amethyst on a strand of hair. If the human eye can see a double image of the hair through the amethyst, it's natural amethyst, mainly due to birefringence.
9. Thermal conductivity test: Adjust the thermal conductivity meter to green (4 bars). Natural amethyst will rise to yellow (2 bars), while fake amethyst will not rise, or only rise to yellow (1 bar) if the area is large.
