State and briefly explain any four physical properties of minerals.
Minerals have distinguishing physical properties that in most cases can be use to determine the identity of the mineral. Among the various properties crystal, habit, cleavage, hardness, density, luster, streak color, tenacity, magnetism and taste.
Individual Crystals:
i) Cubic: cube shapes
ii) Octahedral: shaped likes octahedrons,
iii) Tabular: rectangular shapes examples – feldspar
iv) Equant: a term used to describe minerals that have all of boundaries of approximately equal length.
v) Acicular: long slender needle like crystals, example – natrolite
vi) Prismatic: Abundance of prism faces
vii) Bladed: like a wedge or knife blade example – kyanite
Cleavage: Crystals often contain planes of atoms along which the bonding between the atoms is weaker than along other planes.
Parting: parting is also a plane of weakness in the crystal structure but it is along planes that are weakened by some applied force.
Fracture: If the mineral contains no planes of weakness it will break along random directions called fracture several different kinds of fracture patterns are observed:
i) Conchoidal fracture
ii) Fabrous and splintery
iii) Hackly
iv) Even or regular
v) Uneven or Irregular
Hardness: hardness is determined by scratching the mineral with a mineral or substance of known hardness.
Tenacity: Tenacity is the resistance of a mineral to breaking, crushing, or bending.
i) Brittle: breaks or powder
ii) Malleable : can be hammered into thin sheet
iii) Sectile: can be cut into thin sheeting with knife.
iv) Ductile: bends easily and does not return to its original shapes.