The earth consists of various kinds of elements. The elements in the earth’s crust are rarely found individually and usually are combined with numerous impurities. These substances are called Minerals in Geography Class 11: Minerals.

• The substance that is made of naturally occurring organic and inorganic substances is called minerals. Minerals have different atomic structures, chemical compositions, and physical properties.
• Single element minerals are sulfur, copper, silver, gold, graphite, etc. are found. But it may be made of two or more elements.

ELEMENTS OF EARTH CRUST

• Major elements- The total crust of Earth is made up of mainly eight-elements. They are-
  • Oxygen,
  • Silicon,
  • Aluminum,
  • Iron, 
  • Calcium, 
  • Sodium, 
  • Potassium, and
  • Magnesium.

• Minor Elements – The remaining 2% of the earth’s crust is incorporated with minor elements. They are (i)titanium, (ii)hydrogen, (iii)phosphorus, (iv)manganese, (v) sulfur, (vi)carbon, (vii)nickel, and other elements.
• More than 2000 elements have been found and named. Many of them are related to six major mineral rocks. These six major mineral groups are called major rock-forming minerals.
• The basic source of all minerals: Hot magma is considered as the origin area of minerals. It is found in the inner recesses of the earth. On cooling, the mineral crystal appears on the magma. Several sequences of crystals will lead to the formation of rocks. By the process of solidification, magma turns out into rocks. 

PHYSICAL CHARACTERISTICS OF MINERALS.

• External Crystal form – It is decided by the inner arrangement of the molecules such as cube, hexagonal prisms, octahedrons, etc.
• Cleavage – The propensity to shatter in given directions on a plane surface. It is because of the arrangement of the inner molecules. Cleavage may happen in minerals in more than one direction or at any angle.
• Fracture – It happens when there are no planes, and the inner arrangement of the molecules is complex. The crystal will shatter irregularly.

LUSTRE

• Lustre – metallic, silky, and glossy are some of the typical lustre possessed by minerals. It represents the look of minerals irrespective of the color.
• Colour – The feature of the mineral can be found by the molecular structure such as malachite, azurite. Impurity minerals can also be found by color. For example- graphite.
• Streak – It represents the mineral ground powder color. The color of the Malachite mineral is bright green, But the streak color is light green. The color of fluorite is purple and green, but the steak color is white.

Transparency 

1. Transparent- The beam of light can easily penetrate through an object.
2. Translucent – The beam of light will get diffused in the object.
3. Opaque – The beam of light will never pass.

• Structure – Particular arrangement of a single crystal such as delicate, medium, and coarse texture.
• Hardness – It represents the relative resistance while getting scratched. There are ten minerals listed based on the degree of hardness. They are (i) talc, (ii) gypsum, (iii) calcite, (iv) fluorite, (v) apatite, (vi) feldspar, (vii) quartz, (viii) topaz, (ix) corundum, (x) diamond. 2.5 is the degree of hardness of the fingernail, and 5.5 is the degree of hardness of the knife.

• Specific gravity – The ratio between the heaviness of a given object and the heaviness of a similar volume of water.

Metallic minerals – A mineral content trace of metal. They are divided into three categories-

• Precious metals- (i) gold, (ii) silver,(iii) platinum
• Ferrous metals – Ferrous metals contain iron and are used to produce a different variety of steels. 
• Non-ferrous metals – (i) copper, (ii) steel, (iii) zinc, (iv) tin, (v) aluminium.

Non- metallic minerals – It won’t have any trace of metals. Examples of nonmetallic minerals are

(i) Sulphur

(ii) Phosphate