Minerals

• Minerals

  • 3500 known minerals
  • minerals combine to form all rocks on Earth
  • rock types are dependent on mineral composition
• Characteristics to be identified as Minerals

  • Naturally-occurring

  • Inorganic

  • Homogeneous solid

  • Definitive Chemical composition

  • Ordered internal Structure
• NATURALLY-OCCURING

  • made by natural, specific geologic process/es
  • Precipitation from solution
  • Surface water (halite)
  • Groundwater (calcite)
  • Hydrothermal solution (sulfur)
  • Sublimation from a gas (sulfides)
  • Crystallization from a melt or other liquid (olivine)
  • Solid state growth
  • Solid-liquid or solid-gas reactions
• INORGANIC

  • organic compounds are not considered minerals
  • compound secreted by organisms are not considered minerals, unless geological processes are involved
  • marine animals secrete inorganic chemicals such as carbon carbonate, geologist do not consider them minerals unless it had undergone geologic processes such as burial and lithification
• HOMOGENEOUS SOLID

  • Must be solid at temperatures normally experienced at the earth’s surface
  • Mercury is an exception since it has been listed as a mineral before the establishment of rules defining a mineral
• DEFINITIVE CHEMICAL COMPOSITION

  • a mineral can be represented by a determinable and precise formula
  • a mineral can exist as:

  1. A single mineral (gold - Au, mercury - Hg)
  2. Simple salts (halite – NaCl, sylvite – KCl)
  3. Complex compounds (Apatite - Ca5(PO4)3(OH), turquoise - Ca5(PO4)3(OH)
• DEFINITIVE CHEMICAL COMPOSITION

  • Allotropism – same elemental composition but different minerals
  • • Both graphite and diamond has same composition but formed in different environment
  • Polymorphism – ability of a specific chemical substance to crystallize in more than configuration, dependent upon changes in temperature, pressure, or both
  • • Al2SiO5 forms differently depending on the temperature or pressure it forms
• ORDERED INTERNAL STRUCTURE

  • Minerals have crystalline structure from orderly arranged atom with repeating structural units
• Identify the structure

  A) quartz

  
• Identify the structure

  A) tridymite

  
• Identify the structure

  A) cristobalite

  
• Identify which chemical composition is which

  • they have the same composition but formed in different environment

  A) graphite

  B) diamond

  
• MINERALOIDS

  • Mineral-like with no definite chemical composition or amorphous (no ordered crystalline structure)
  • obsidian (volcanic glass)
  • opal
• PROPERTIES OF A MINERAL

  • minerals have definitive set of characteristics that define a mineral
  • minerals are universal (quartz found on earth has the same property as the quartz found in Venus)
  • some characteristics can be helpful in identifying a mineral such as hardness and/ or color
• COLOR

  • caused by the absorption, or lack of absorption, of various wavelength of light
  • can be a diagnostic property for minerals existing in one shade of color some minerals changes color depending on impurities caused by chemical substitution such as quartz
• Iridescence - play of colors where the color changes depending on the angle it is viewed
• Color also changes due to chemical reaction such as tarnishing or oxidation
• STREAK

  • the color of the powdered form of a mineral
  • unlike color, streak is a consistent property of a mineral
  • to determine streak, scratch the mineral to a harder mineral
• HARDNESS

  • mineral’s measure to resistance to abrasion or scratching
• Identify the 10 index minerals

  A) Talc

  B) Gypsum

  C) Calcite

  D) Fluorite

  E) Apatite

  F) Orthoclase

  G) Quartz

  H) Topaz

  I) Corundum

  J) Diamond

  
• Identify the crystal habit

  Banded

  
• Identify the crystal habit

  Bladed

  
• Identify the crystal habit

  Cubic

  
• Crystal habit

  • the common shape of a crystal or aggregates of crystals
• • CLEAVAGE - tendency of a mineral to break in particular orientations due to zones of weakness in the atomic bond of its crystal structure
  • Fractures or irregular breakages occur when the bond strengths in a crystal structure is almost equal in all directions.
• LUSTER

  • the ability of minerals to reflect light

  1. Metallic -bright, reflective
  2. Nonmetallic -dull, reflective
  3. Submetallic
• DIAPHANEITY

  • describes how well light passes through a mineral
  • transparent, translucent, opaque
• SPECIFIC GRAVITY

  • Ratio of the volume of a substance and the weight of the same volume of water
  • A mineral with a SG of 2 means that it is 2x heavier compared to water o the same volume
• Other physical properties of minerals

  • Magnetism - natural power of some objects and substances Magnetite (Fe3O4)
  • Taste – Halite (NaCl)
  • Effervescence – reaction to acid Calcite (CaCO3)
  • Odor – Sulfur (S)
  • Fluorescence – Calcite (CaCO3)
• MINERAL CLASSICIFICATION

  • can be classified as 1.) silicates and 2. non-silicates
• SILICATES

  • Largest group of minerals

  • Made up of compounds containing silicon and oxygen

  • Silicon tetrahedron: building blocks of silicates
• Non-silicates

  • minerals without silicon
• ECONOMIC IMPORTANCE OF MINERALS

  • Ore - Useful/profitable metallic (and some nonmetallic) minerals that can be extracted, and which contain useful substances
  • Gemstones - well-formed minerals and/or mineraloids which are cut and polished for jewelry and other aesthetic purposes.
• The Philippines is the 5th most mineralized country

  in the world metallic resources:

  • 3rd in Gold reserves
  • 4th in Copper
  • 5th in Nickel
  • Others: Chromite, Silver, Iron, Cobalt, Manganese (MGB, 2010)
• almost 95% of rocks are composed of less than 100 minerals