Mineralogy

• Physical Properties


  Intrinsic characteristics of minerals that can be observed, measured, or described without altering the mineral's chemical composition
• Optical Properties


  Properties like behavior towards light that require extremely thin sections of minerals through which light can pass and are best studied with the help of a microscope
• Chemical Properties


  Properties involving chemical analysis of the minerals to know their constituents, qualitatively and quantitatively
• Color


  The appearance of the particular object in light (darkness destroys color). A particular color is produced by reflection of some and absorption of other components of white light.
• Types of Mineral Color

  • Idiochromatic
  • Allochromatic
  • Pseudochromatic
• Luster


  The way a mineral reflects light. It depends on the refractive index, absorption capacity, and nature of the reflecting surface.
• Types of Mineral Luster

  • Metallic
  • Adamantine
  • Vitreous
  • Pearly
  • Silky
  • Resinous
  • Dull
• Streak


  The color of the finely powdered mineral as obtained by scratching or rubbing the mineral over a rough unglazed porcelain plate
• Colorless and transparent minerals will always give a colorless streak that has no significance
• The colored and opaque minerals, especially of ore groups, give typical characteristic streaks quite different from other similar looking minerals
• Mohs Hardness Scale


  A scale from 1 to 10 that measures the resistance a mineral offers to scratching, abrasion, rubbing or indentation
• Mohs Hardness Scale


  • 1 Talc
  • 2 Gypsum
  • 3 Calcite
  • 4 Fluorite
  • 5 Apatite
  • 6 Orthoclase
  • 7 Quartz
  • 8 Topaz
  • 9 Corundum
  • 10 Diamond
• Cleavage


  The tendency of a crystallized mineral to break along certain definite directions yielding more or less smooth, plane surfaces
• Cleavage planes are the planes of easiest fractures, and are essentially indicative of directions of least cohesion in the atomic constitution of a mineral
• Fracture


  The appearance of the broken surface of a mineral in a direction other than that of cleavage
• Types of Fracture

  • Even
  • Uneven
  • Conchoidal
  • Splintery
  • Hackly
  • Earthy
• Tenacity


  The behavior of a mineral towards the forces that tend to break, bend, cut or crush it
• Types of Tenacity

  • Sectile
  • Brittle
  • Flexible
  • Flexible and elastic
  • Plastic and elastic
• Structure (Form)


  The physical make up of a mineral, expressed by the habit in which the crystal or crystalline substance tends to occur in nature
• Types of Mineral Structure

  • Tabular
  • Elongated
  • Bladed
  • Lamellar
• Structure


  The physical make up of a mineral, often helpful in identifying a particular mineral. It shows the habit in which the crystal or crystalline substance making a mineral tends to occur in nature.
• Bladed

  • Kyanite
• Lamellar

  • Vermiculite
• Folliated

  • Muscovite (mica)
• Fibrous

  • Asbestos
  • Gypsum
• Radiating

  • Iron pyrites
• Granular

  • Chromite
• Globular

  • Hematite
• Reniform

  • Hematite
• Mammillary

  • Malachite
• Specific gravity


  The ratio between the density of a mineral and that of water at 4° Celsius. It has no units.
• Density (hence specific gravity) of minerals depends primarily on composition and atomic constitution
• Temperature and pressure can change a mineral's volume, density and specific gravity
• Specific gravity of some common minerals

  • Quartz (2.65)
  • Calaite (2.60)
  • Fluorite (3.18)
  • Hematite (5.2)
  • Chalcopyrite (4.2)
  • Galena (7.5)
  • Native gold (19.3)
• Form


  The internal atomic arrangement of a mineral which is manifested outwardly by development of geometrical shapes or crystal characters
• Forms of minerals

  • Crystallized
  • Crystalline
  • Amorphous
• Crystallized


  Mineral occurs in the form of well-defined crystals as represented by crystal faces and angles, or shows perfect cleavage
• Crystalline


  Well-defined crystals are absent but the mineral shows a clear tendency towards crystallisation as evidenced by development of small grains each of which is virtually an incipient crystal
• Amorphous


  Neither a crystal face nor a cleavage is seen. There is no evidence of orderly arrangement of atoms