Geo_Crystal-Quartz

• Crystallography


  The branch of science that deals with the study of structure, geometry and properties of crystals
• Types of symmetry in crystals


  • Plane of symmetry
  • Centre of symmetry
  • Axis of symmetry

  
• Plane of symmetry


  An imaginary plane which passes through the centre of a crystal and divides it into two equal portions which are exactly the mirror images of each other

  
• Centre of symmetry


  An imaginary point in the crystal that any line drawn through it intersects the surface of the crystal at equal distance on either side
• Axis of symmetry


  An imaginary line, passing through the crystal such that when the crystal is rotated about this line, it presents the same appearance more than once in one complete revolution

  
• Symmetry elements


  The locations where the symmetry operations occur such as rotation axis, a mirror plane, an inversion center, or a translation vector

  
• Symmetry


  A set of mathematical rules that describe the shape of an object

  
• There is only one object in the geometrical universe with perfect symmetry - a sphere
• Crystal systems


  • Isometric (or cubic)
  • Tetragonal
  • Orthorhombic
  • Hexagonal
  • Triclinic
  • Monoclinic
  • Rhombohedral (trigonal)
• Isometric (or cubic)


  All three axes are equal in length, and all are perpendicular to one another
• Tetragonal


  Two of the three axes are equal in length, and all three axes are perpendicular to one another
• Orthorhombic


  All three axes are unequal length, and all are perpendicular to one another
• Hexagonal


  Of four axes, three are equal length, are separated by equal angles, and lie in the same plane. The fourth axis is perpendicular to the plane of the other three axes. Hexagonal cells have lattice points in each of the two six-sided faces.

  
• Triclinic


  All three axes are unequal in length, and none is perpendicular to another
• Monoclinic


  All three axes are unequal in length, and two axes are perpendicular to another
• Rhombohedral (trigonal)


  All three axes are of equal length, and none of the axes is perpendicular to another, but the crystal faces all have the same size and shape
• In crystallography, symmetry is used to characterize crystals, identify repeating parts of molecules, and simplify both data collection and nearly all calculations
• Quartz


  Composed of silicon (Si) and oxygen (O), the two most abundant elements in the crust of the Earth, an essential mineral in such silica-rich felsic rocks as granites, granodiorites, and rhyolites
• Chalcedony


  The most generally widespread of these materials is composed of tiny fibers of silica
• Jaspers


  Solid-colored materials mostly chalcedony stained by oxides
• Agate


  Banded varieties, or materials with mosslike inclusions
• Piezoelectric


  A crystal develops positive and negative charges on alternate prism edges when it is subjected to pressure or tension. The charges are proportional to the change in pressure.
• Common applications of quartz


  • Glass and ceramics manufacturing
  • Foundry molds in metal casting
  • Abrasive in sandpaper
  • Silica sand in sandblasting
  • Whetstones, millstones, and grindstones
• Forms of quartz


  • Alpha quartz (low quartz, stable up to 573°C)
  • Beta quartz (high quartz, stable above 573°C)
• Types of quartz


  • Rock quartz
  • Milky quartz
  • Brown quartz
  • Yellow quartz
  • Amethyst
  • Rose quartz
  • Quartzite
  • Dumortierite
  • Amethyst-citrine