IS1 - MINERALS

• Minerals


  Building blocks of rocks
• All the physical properties of a mineral result from the mineral's internal arrangement of atoms
• Color


  A visual attribute based on perception, not very reliable as many minerals can occur in different colors
• Streak


  The color of a mineral in its powdered form, the true color of the mineral
• Hardness


  A measure of the resistance of a mineral to being scratched, determined by scratching two minerals against each other, using the Mohs Hardness Scale
• Mohs Hardness Scale

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


  The tendency of a mineral to cleave, or break, along flat, even surfaces, in one, two, or more directions
• Types of Fracture


  • Conchoidal (curved surface, shell-like or broken glass)
  • Hackly (sharp, jagged surface or edges)
  • Fibrous (appearance of many fine threads lying parallel)
  • Uneven/Irregular (rough surface or one with random irregularities)
• Luster


  How light is reflected off a surface of a mineral, can be metallic or nonmetallic
• Types of Nonmetallic Luster

  • Vitreous or glassy (reflective properties like glass)
  • Resinous (similar to the reflective properties of a resin or amber)
  • Pearly (similar to the inside of a mollusk shell or a pearl)
  • Earthy or Dull (rough texture and poor reflective properties)
  • Waxy (appears as if coated with wax)
  • Silky (fine, fibrous form or habit)
  • Adamantine (brilliant looking minerals with high index of refraction)
• Density and Specific Gravity


  Specific gravity is the ratio of the mineral's density to the density of water, metallic minerals are denser and have higher specific gravity
• Special Properties of Minerals

  • Distinct Odor
  • Magnetism
  • Taste
  • Effervescence with HCl
  • Fluorescence
  • Feel
• The Mohs Hardness Scale is used to determine the relative hardness of minerals based on their ability to scratch other minerals.
• Minerals have a crystalline structure and can be identified by their physical properties such as color, luster, hardness, cleavage, fracture, specific gravity, streak, solubility, and optical properties.
• Criteria to be a mineral

  1. naturally occurring
  2. inorganic
  3. solid
  4. definite chemical composition
  5. orderly internal structure
• fracture -

  the irregular uneven breakage of a mineral