Rocks

Topics: Igneous rock, Sedimentary rock, Metamorphic rock Pages: 3 (977 words) Published: September 20, 2013
At a granular level, rocks are composed of grains of minerals, which, in turn, are homogeneous solids formed from a chemical compound that is arranged in an orderly manner. The aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed. Many rocks contain silica (SiO2); a compound of silicon and oxygen that forms 74.3% of the Earth's crust. This material forms crystals with other compounds in the rock. The proportion of silica in rocks and minerals is a major factor in determining their name and properties.[2] Rocks are geologically classified according to characteristics such as mineral and chemical composition, permeability, the texture of the constituent particles, and particle size. These physical properties are the end result of the processes that formed the rocks.[3] Over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock: igneous, sedimentary, and metamorphic. The three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks. By increase or decrease in the proportions of their constituent minerals they pass by every gradation into one another, the distinctive structures also of one kind of rock may often be traced gradually merging into those of another. Hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series.[4] Igneous

Main article: Igneous rock

Sample of igneous gabbro
Igneous rock (derived from the Latin word igneus meaning of fire, from ignis meaning fire) forms through the cooling and solidification of magma or lava. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Essay about Formation of Rocks
  • History of Rock Essay
  • Igneous Rocks Essay
  • Rock Formation Essay
  • History of Rocks Essay
  • The Formation of Rocks in Ireland Essay
  • The Different Types of Rocks Essay
  • Igneous Rocks Essay

Become a StudyMode Member

Sign Up - It's Free