Cochise College          Photos of Minerals

                          Geology Home Page                

                          Roger Weller, geology instructor

                          wellerr@cochise.edu
                                  copyright 2011-R.Weller
 

Mineral Information on:
quartz


Chemical Group:    oxide

Chemical Formula:   
SiO2

Color: colorless, white, pink, purple, brown, red, yellow, black, etc.                                                                         

 

Hardness:  7          Specific Gravity:   2.65                 Fracture: conchoidal

Cleavage:   none      Luster:  vitreous (cryptocrystalline quartz ranges from waxy to dull)

 

Crystal Forms: Trigonal system
     Crystals are commonly hexagonal prisms, capped with 3 large rhombohedral faces
     and three small rhombohedral faces.
     Quartz also forms twinned crystals; the most famous are Japanese twins where
     two flattened quartz crystals are attached at right angles to each other.

Special properties: piezoelectric and pyroelectric

Mineral Associations:  Quartz is found where aqueous solutions have deposited it
in fractures and volcanic vesicles.

Identifying Characteristics:  hardness 7, resistant to chemical weathering

Uses:  gemstones, making glass, abrasives

Occurrences:  just about everywhere.  Nice crystals come from Brazil and Switzerland;
     in the USA from Arkansas, Colorado, New York, Idaho, New Mexico

Toxicity:      when-swallowed- low          when inhaled- high

Additional Information:
Transparent quartz gemstones:  amethyst (purple), citrine (yellow),
     smoky quartz (brown to black), rock crystal (colorless).
     ametrine (purple and yellow)
Translucent gemstones: agate, aventurine, chalcedony, chrysoprase,
     jasper, tigereye, bloodstone, carnelian, sard, onyx
Other common forms: milky quartz, chert, flint, rose quartz