Quartz is not a rock at all; it is a mineral made of silicon dioxide (SiO₂).

Quick Scoop

  • Quartz is a mineral, not a rock, with the chemical formula SiO₂.
  • It is one of the most abundant minerals in Earth’s crust and appears in many different rock types.
  • Quartz can be the main ingredient in certain rocks, like quartzite (metamorphic) and some sandstones (sedimentary).

Quartz vs. Rock

  • A mineral is a single naturally occurring inorganic substance with a specific composition and crystal structure; quartz fits this definition exactly.
  • A rock is made of one or more minerals, so rocks such as granite, sandstone, and quartzite often contain lots of quartz but are classified as igneous, sedimentary, or metamorphic rocks, not “quartz rocks.”

Where Quartz Shows Up

  • In igneous rocks, quartz is a major component of granites and rhyolites, especially in silica-rich (felsic) compositions.
  • In sedimentary rocks, quartz grains dominate many sandstones and siltstones, and with metamorphism these can turn into quartzite, which is a rock almost entirely made of quartz.

Simple Answer To Your Title Question

If someone asks, “What type of rock is quartz?” the precise answer is:

  • Quartz is a mineral , not a rock.
  • However, there are rocks (like quartzite and quartz sandstone) that are composed mostly of quartz and are classified as metamorphic and sedimentary rocks, respectively.

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