Date: December 13, 2014


Following are the major elements of earth crust –

  1. Oxygen 46.6% 2. Silicon 27.7% 3. Aluminium 8.1%      4. Iron 5%        5. Calcium 3.6%
  • Magma which is found in the interior of earth, is the source of all minerals. Coal, Petroleum and Natural Gas Hydro Carbons.

Major Minerals :

  1. Feldspar – In all Feldspars, Silicon and Oxygen are present while other elements occur in different feldspar. Half of the crust is made up of Feldspar. These are used in glass and utensils.
  2. Quartz – Major component of silica and granite. Used in Radio and Radar, white or colourless.
  3. Pyroxene - Calcium, Iron, Magnesium and Silica are included. These are 10% of crust. Found in the Meteorites.
  4. Amphibole – 7% of earth crust. Aluminium, Silica, Iron, Calcium are major elements. Used in Asbestos industry. Hornblend is also Amphibole.
  5. Mica – 4% of crust. Potassium, Aluminium, Iron, Silica are major elements. These are used in electronic devices and are found in igneous. Metamorphic rocks.
  6. Allvieen – Magnesium, Iron, Silica are major components found in Basaltic rocks and used in Jewellery.

In the metallic elements precious metals (Gold, Silver), Iron and Non-Iron metals are included. Non iron elements copper, lead, zinc and tin are included.


  • The study of rock is called Petrology. The rocks are of three types viz. Igneous, Metamorphic and Sedimentary rocks.
  • Igneous Rocks - When magma cools and solidifies, it form igneous rocks. Granite, Grabo, Basalt, Volcanic Bracia are igneous rocks.
  • Sedimentary Rocks – Rocks on the crust get fragmented in different shapes by weathering agents. Exogenic Agents carries and deposits them. Due to close and dense gathering of these fragments, they got convert into rocks and the process is known as Lithification. These rocks are mechanically formed (Shale, Lime) originally formed (Limestone, coal) and chemically formed (Potash, Gypsum).
  • Metamorphic Rock – These rocks are due to the change in pressure, volume and temperature. The rocks are re-crystallized during metamorphism and there is rearrangement in the parent rock. Some rock particles or minerals get themselves systematically arranged in lines or over surface. This is known as ‘Foliation’. Granite, State, Marble, Quartz, Schist are example.
  • Rock Cycle – This is a continuous process in which old rocks get new form. Igneous rocks are the primary rocks and both metamorphic and sedimentary rocks are made up of them. Igneous and metamorphic rocks found sedimentary rocks. The rocks on the earth crust went towards interior of earth where due to intense heat they get melt and change into Magma which is ultimately the source of Igneous rocks.