Amethyst is one of the most precious and valuable stones belonging to the quartz group of minerals. It is the official birthstone for February. Since purple is considered to be one of the royal colors, amethyst has a historical importance as an insignia of power. Fine amethysts are featured in the British Crown Jewels and they were also a favorite of Catherine the Great and Egyptian royalty. Amethyst is harder than most other materials, so it is very resistant to wear and tear.