The most common member of the SiO2 group of the tectosilicates. Quartz comes in many varieties. Gold is often found
in quartz veins.
| variety |
color |
impurity |
| amethyst |
purple |
Fe+4 |
| blue quartz |
blue |
FeTiO3 (precipitate) |
| chalcedony |
|
|
| chrysoprase |
|
|
| citrine |
yellow |
Fe+3 |
| jasper |
red |
|
| "rock crystal" |
colorless |
Al, Ge |
| rose |
rose red |
? |
| smoky |
black |
metaminctization |
When large samples of quartz are examined, it is found that 50.5% is left-handed, while 49.5% is right-handed. The two
may be differentiated by the position of a small face in relation to the large rectangular faces. If the small face is on
the left, the crystal is left handed, and if it is on the right, the crystal is right-handed. The reason the left-handed
quartz should form more predominantly is not known. | 
