Mohs Hardness of 7 with a trigonal crystal structure.
Crystalline Quartz is the general stone which we call Amethyst. As Amethyst it ranges in color from lilac to deep purple. The deeper colors are generally more valuable, and at one time were more valuable than diamonds. The actual crystal hold the properties for Citrine as well.
Amethyst is mined in Brazil, Uruguay, Bolivia and Argentina, as well as in several African countries. Generally, larger sizes are to be found in South America although Africa is reputed to have the more sought after deeper color in smaller sizes. The darker Amethyst, more often in smaller sizes is also found in Australia.