Minerals and Rocks

• A mineral is:

  1.A naturally occurring,

  2. Inorganic

  3. Solid

  4. That has a definite chemical composition

  5. A definite crystal structure
• 1. Graphite – pencil lead, batteries
  2. Sulfur – matches, fireworks
  3. Talc – Powder, ceramics
• not minerals: cement, steel (man-made)
• INORGANIC - NOT COMPOSED OF ORGANIC MATTER; NOT FROM LIVING THINGS OR THE REMAINS OF LIVING THINGS.
• ➢ Coal is NOT a mineral because it comes from plants

  ➢ Amber is NOT a mineral because it comes from tree sap

  ➢ Pearls is NOT a mineral because it comes from oysters
• SOLIDS

  -Have a definite volume and a definite shape.

  -Stable and solid at room temperature
• Mercury is not a mineral because it is liquid at room temperature
• CHEMICAL COMPOSITION

  Silicate Minerals

  Non-silicate minerals
• Silicate Minerals

  • Silicon and oxygen groupings.
  • Combined with one or more metals
  • Largest group of the minerals (90% of earth’s crust)
• Non-silicate minerals

  b) DO NOT contain SiO2

  1. subdivided into several other classes
  2. Extremely rare
  3. 8% of the Earth's crust
  4. Few are relatively common

  ➢ calcite
• NON-SILICATE SUBDIVISIONS

  • Native Elements
  • Sulfides
  • Sulfates
  • Oxides
  • Halides
  • Carbonates
• Native Elements –elements found in nature in their mineral form.

  ➢ gold (Au), sulfur (S), silver (Ag)
• Sulfides – minerals that contain sulfur ions.

  ➢ Galena (PbS), Pyrite (FeS2)
• Sulfates - minerals which include the sulfate ion (SO42-).

  ➢ Gypsum (CaSO4·2H2O)
• Oxides - minerals that contain oxygen bonded with one or more metals

  ➢ Hematite (Fe2O3), Magnetite (Fe3O4)

  ➢ minerals containing (OH) are typically included in this class. (hydroxides).

  ➢Portlandite (Ca(OH)2)
• Halides - minerals with that contain Fluorine, Chlorine, Bromine and Iodine ions.

  ➢ Halite (NaCl), Fluorite (CaF2)
• Carbonates – minerals that contain a carbonate ion, CO2−3.

  ➢ Calcite (CaCO3), Dolomite (CaMg(CO3)2)
• CRYSTAL STRUCTURE

  1. The internal structure or arrangement of atoms within a mineral

  ➢ Halite (NaCl)

  2. Atoms/molecules are arranged in repeating geometric patterns.
• Six basic crystal system

  Cubic - Galena, Halite, Pyrite

  Tetragonal – Chalcopyrite

  Hexagonal - Quartz, Calcite

  Orthorhombic - Olivine, Topaz

  Monoclinic – Mica, gypsum

  Triclinic – Feldspar, Turquoise
• MINERAL FORMATION

  Minerals form

  1. When lava or magma cools to solidification.
  2. When water evaporates and leaves minerals remain.
  3. When water is supersaturated with a mineral; minerals will settle out of the water and deposit as a precipitate.
• Minerals can be identified by their physical and chemical characteristics

  A.Physical Properties:

  ➢Color

  ➢Streak

  ➢Luster

  ➢Hardness

  ➢Cleavage or Fracture

  ➢Density
• Minerals can be identified by their physical and chemical characteristics.

  B.Chemical Properties

  ➢ Specific and unique for each mineral

  ➢ Determined by chemical composition and structure
• Color: Not a reliable property; some minerals can be many different colors.

  Color may vary due to:

  1. Natural coloring agents - impurities
  2. Weathering; exposure to the environment
• Streak: The color of the mineral in its powdered form.

  a)Determined by using a streak plate

  1. Quartz: White/colorless
  2. Hematite: reddish brown
• Luster: The way a mineral shines/reflects light from its surface.

  a)Metallic: reflects light like the surface of a polished metal.

  1. Galena, Pyrite, Graphite, Magnetite...

  b) Non Metallic: reflects light in more subtle ways

  1. Pearly-Mica

  2. Dull/Earthy-Bauxite

  3. Brilliant-Diamond

  4. Glassy-Quartz

  5. Waxy-Talc
• Hardness: A measure of how easily a mineral can be scratched.

  1. Determined by a minerals internal structure.

  b) When a mineral is scratched by a substance; it is softer than the substance

  c) When a mineral scratches a substance; it is harder than the substance
• Cleavage: When a mineral splits/breaks along smooth flat surfaces

  1. Mica - One direction; sheet
  2. Galena – Three; cubic shape
• Determined by atomic structure of mineral.

  1. Cleavage is the way a mineral breaks
  2. Crystal Shape is the way crystal grows
• • Cleavage in one direction - muscovite
  • Cleavage in two direction - feldspar and calcite
  • Cleavage in three direction - Halite
• Fracture: When a mineral breaks unevenly into curved or irregular pieces with a rough and jagged surfaces.
• Density or Heft: Minerals have different densities, and vary in weight given the same sample size.

  ➢ How heavy the mineral feels in your hand
• Effervescence

  1. Calcite reacts with HCl; bubbles of CO2
• Oxidation:

  Reaction between Iron (Fe) and oxygen (O2).

  1. Iron (Fe) + oxygen = Rust ➢Metal is weakened by change
• Reaction between copper and air; creates a greenish coating

  1. Copper (Cu) + oxygen = copper oxide
  2. metal is not weakened; pennies