lec. 5: mineralogy

• mineralogy

  • is the systematic study that deals with the characteristics of minerals.
• mineralogy

  • scientific discipline that is concerned with all aspects of minerals including their physical properties, chemical composition, internal crystal structure occurence and distribution in nature, and their origins in terms of physicochemical conditions of formation.
• crystallography

  • study crystal forms, forms in which the minerals crystallize, as well as their internal structure, relations and distribution of atoms, ions or ionic groups in crystal lattice.
• physical mineralogy

  • study of physical properties of minerals, such as cohesion(hardness, cleavage, elasticity and density) and so on.
• chemical mineralogy

  • study of chemical formula and chemical properties of the minerals
• environmental mineralogy

  • studies complex and very different conditions of the origin of the minerals and mitigates potential contamination problems
• descriptive mineralogy

  • deals with the classification of minerals into groups based on their common properties, mostly chemical and structural properties.
• crystal system

  • method of classifying crystals according to their atomic lattice or structure. the atomic lattice is the 3 dimensional network of atoms that are arranged in symmetrical pattern.
• cubic system

  • also known as the isometric system. all three axes are of equal length and intersects at right angles.
  • based on a square inner structures
  • diamond, gold, silver
• tetragonal system

  • two axes are of equal length and are in the same plane, the main axis is either longer or shorter and all three intersects at right angles.
  • based on a rectangular inner structure
  • zircon
• hexagonal systems

  • three out of the four axes are in one plane, of the same length, and intersects each other at angles of 60 degrees. the 4th axis is of different length and intersects others at right angles.
  • based on a hexagon inner structure
  • aquamarine, emerald
• trigonal system

  • axes and angle in this system are similar to hexagonal system, and the two systems are often combined as hexagonal. in cross section of a trigonal crystal, there wil be three sides.
  • based on a triangular inner structure
  • amethyst, citrine, ruby, quartz, sapphire
• orthorhombic system

  • three axes, all if different lengths, are at right angles to each other
  • based on rhombic/diamond inner structure
  • alexandrite, topaz
• monoclinic system

  • there are three axes, each of different lengths, two are at right angles to each other and the third is inclined.
  • based on a parallelogram inner structure
  • azurite, gypsum, serpentine
• base-centered monoclinic

  • lattice points in the middle of each of the two ends
• triclinic system

  • all three axes are of different length and inclined towards each other
  • based on a triclinic inner structure. 3 inclined angles.
  • amazonite, turquoise.
• hardness

  • the ability to resist being scratched.
  • determined by the ability of one mineral to scratch another.
• luster

  • how mineral reflects light
  • minerals that dont exhibit luster are called earthy, chalky, dull
• streak

  • streak is the color of the powdered mineral which is more useful for identification than the color of the whole mineral sample
• color

  • one of the most obvious properties of a mineral is a color. color should be considered when identifying mineral but should never be used as the major identifying characteristics
• specific gravity

  • the ratio between the mass of the mineral and the mass of water
  • SG = mineral mass / water mass
• cleavage

  • the way in which a mineral breaks along smooth flat planes are called cleavage which occur in the plane of weakness in mineral's structure
• fracture

  • when mineral breaks irregularly, the breaks are called fractures
  • can be grainy, hackly (jagged), conchoidal or splintery
• tenacity

  • how well a mineral resist breakage
• other diagnostic characteristics

  • transparency
  • translucency
  • opaqueness
  • taste
  • acid reaction
  • magnetism
  • crystal shape
• rock forming minerals

  • scientist have identified over 4000 different minerals. a small group of these minerals make up almost 90 percent of the rocks of the earths crust.
• most abundant minerals in earths crust

  • feldspar
  • quartz
  • pyroxenes
  • nonsilicates
  • amphiboles
  • micas
  • clays
  • other silicates
• feldspar

  • rock form minerals that make up almost 60 percent of the earths crust, most abundant mineral in the earths crust
  • occurs in all classes of rocks, most common in igneous rocks - formed from crystallization of magma
  • monoclinic/triclinic
  • used in different industries such as glass and ceramics
• quartz

  • second most abundant mineral in eaths crust next to feldspar
  • widely distributed mineral primarily composed of silicon dioxide
  • with great economic performance - varieties include gemstones such amethyst, citrine
  • used in manufacture of glass and ceramics