By Gabriella Arendes

Types of Rocks

All rocks are composed of minerals, rocks are classified by the way that they are formed and where they are formed. There are three types of rocks, Igneous, Sedimentary and metamorphic rocks.

Example of rocks


  • Intrusive; forms in side the Earths, cools slowly
  • Coarse, 1mm to 10mm
  • Non- Vesicular
  • Felsic, light, lower
  • 10% Amphibole
  • 20% Biotite
  • 40% Quartz
  • 20% Potassium Feldspar


  • Inorganic
  • Pebbles, cobbles, and/or boulders embedded in sand, clay, silt
  • Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals
  • Angular fragments


  • Foliated
  • Fine to medium
  • Contains mica, quartz, fledspar, amphibole, pyroxene
  • Regional ( heat and pressure increases)
  • Foliation surfaces shiny from microscopic mica crystals

The Rock cycle

The rock cycle is a model showing how rocks are formed. There are internal processes that occur in Earth and external processes that occur on Earth.