Amethyst

Color: Violet, pale red-violet
Color of streak: White
Mohs’ hardness: 7
Specific gravity: 2.63 – 2.65
Cleavage: None
Chemical composition: Silicon dioxide
Refractive index: 1.544 – 1.553

Amethyst is the most highly valued stone in the quartz group. It is said to have many supernatural powers; it brings luck, ensures constancy, protects against magic and home-sickness. The name (Greek) probably means “not drunken” as amethyst was also worn as an amulet against drunkenness. Crystals are always grown onto a base. 

Heat treatment between 878 – 1382 F / 470 – 750 C produces light yellow, red brown, green or colorless varieties (be careful when soldering). There are some amethysts that lose some color in daylight. The original color can be restored by x-ray radiation.

Found in geodes in alluvial deposits. The most important deposits are in Brazil, Uruguay and the Malagasy Republic. The best stones are faceted, others are tumbled or worked into ornaments. Can be confused with beryl, fluorite, glass, synthetic corundum, kunzite, spinel, topaz and tourmaline. Amethyst is synthesized but not for the jewelry market.