These two examples show the shape of individual quartz crystals.
Click on image for full size
Windows to the Universe Image


Quartz is the second most common mineral in Earthís crust. It is a member of the quartz group, which includes less common minerals such as opal, crystobalite, and coesite.

Silica (Si) and Oxygen (O) are the only elements within pure quartz. If a cooling magma has silica left after feldspars have formed, quartz is likely to form. Because of its low density, even lower than many feldspars, quartz is also like to float in the magma and accumulate in surface rocks.

Quartz can be found in all sorts of rocks. Intrusive igneous rocks sometimes contain large quartz crystals. Metamorphic rocks such as gneiss also have large quartz crystals. Sedimentary rocks such as sandstone are often made of tons of little pieces of quartz crystals. In fact, most sand is made of quartz because it is hard and does not weather away easily. Some pieces of quartz are white like milk but most are clear like glass, sometimes with a little pink or grey tinge of color.


  • Shape: Trigonal (Perfect crystals are usually 6-sided prisms with a pyramid shape at the end. However, it is much more common to find many crystals that have grown in a mass or broken crystals.)
  • Luster: Glassy or greasy
  • Color: Colorless or white. Some varieties are pink or smoky.
  • Streak: White
  • Hardness: 7 on Mohs Hardness Scale
  • Cleavage: None
  • Fracture: Conchoidal

Last modified November 6, 2003 by Lisa Gardiner.

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Element (Chemical Element)

An element (also called a "chemical element") is a substance made up entirely of atoms having the same atomic number; that is, all of the atoms have the same number of protons. Hydrogen, helium, oxygen,...more


Feldspar is the most common mineral in the Earthís crust, so you are very likely to find it in the rocks you collect! It is found it all of the three rock types, but is most common in intrusive igneous...more

Elements in the Earthís Crust

Even though there are 92 elements that naturally occur, only eight of them are abundant in the rocks that make up the Earthís outer layer, the crust. Together, these 8 elements account for 98.5% of the...more

Bowen's Reaction Series

As magma cools slowly, elements within it become chemically bonded forming crystals of minerals. However, not all minerals form at the same time during the cooling process. Some minerals crystallize when...more

Granite Rocks

As granite is an intrusive igneous rock, a close look at a piece of granite will reveal that there are crystals of common silicate minerals within it such as quartz, plagioclase feldspar and orthoclase...more

Whatís That Mineral?

Each type of mineral is made of a unique group of elements that are arranged in a unique pattern. However, to identify minerals you donít need to look at the elements with sophisticated chemical tests....more


Quartz is the second most common mineral in Earthís crust. It is a member of the quartz group, which includes less common minerals such as opal, crystobalite, and coesite. Silica (Si) and Oxygen (O) are...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA