Quartz

Quartz is a crystal appreciated since prehistoric times. The most ancient name recorded is kristallos, recorded by Theophrastus. This name is deprived from two root words that mean "Ice cold" and "solid".
 * Hardness (Mohs Scale) || 7 ||
 * Formula || SiO2 ||
 * System || Trigonal ||
 * Lustre || Vitreous ||
 * Color || multiple (Depends on trace element) ||

= = == http://www.mindat.org/min-3337.html https://www.pinterest.com/halinafuchs/gem-quartz-rose-quartz/