Earth Science Education logo and mountains
Rocks and Minerals of Salt Lake County
Return to minerals

Introducing your friend:

QUARTZ

smokey quartz

The name quartz, is German. We don't know much more than that.

Quartz is composed of:
Oxygen (one part)
Silicon (two parts)

Appearance:
Small crystals look like bits of broken glass.
Larger crystals also look glassy. They seem transparent or dusky.
Crystals glisten, not flash.

Hardness: 7
A quartz crystal will scratch a knife blade. A knife blade will not scratch a quartz crystal.

How to recognize quartz crystals in a rock:
Crystals look like bits of glass or shattered pieces of glass.
Larger crystals look sort of slick.
In sedimentary rocks, quartz grains look like bits of sand.Weathering:
Quartz resists chemical weathering and is susceptible to physical weathering. Therefore, quartz survives the action of weathering processes that destroy most other minerals but weathers into smaller and smaller pieces of quartz until it becomes quartz sand, which is by far the most common kind of sand.

Where you can find quartz in Salt Lake County:

  • As crystals in the igneous rocks of Little Cottonwood Canyon (granites) and igneous rocks of the Oquirrh Mountains.
  • As the quartz of quartzite boulders carried by streams from the Oquirrh Mountains and the Wasatch Range.
  • As the sand grains of the pinkish - red sandstones of Red Butte Gardens east of the University of Utah.
  • As the fine sand grains of the tan beds of the north end of the Oquirrh Mountains near Pleasant Green cemetery.
  • As the loose sand of the sandy soils of Sandy.
  • In most of the igneous, metamorphic and sedimentary tombstones of local cemeteries.


So why is quartz your friend?
90% of the rocks that children hand me are loaded with quartz. So seeing quartz is like seeing a familiar, recognizable, friend. It gives me confidence to start figuring out the rock's story.