Minerals

Minerals What are they? Uses of … Identification Formation of …. Composition Classification Crystal Systems

What is a Mineral? There are five criteria that a substance must meet in order to be considered a mineral. To be a mineral a substance must: There are five criteria that a substance must meet in order to be considered a mineral. To be a mineral a substance must: 1. Be naturally occurring 2. Be inorganic 3. Be solid at room temperature 4. Possess a definite chemical composition 5. Possess a well defined crystal structure

What is a Mineral?  Minerals are naturally occurring. Minerals are never man-made. If a substance that is normally found in nature can be manufactured. The manufactured material is not considered a mineral. Natural Diamond: Synthetic Diamond: Mineral Non-Mineral

What is a Mineral?  Minerals are inorganic substances. This means that they did not form as a result of a biological process. Coal: Not a MineralAmber: Not a Mineral Fossilized Plant Remains Fossilized Plant Resins

What is a Mineral?  Minerals are always solid at room temperature. The majority of metals and non-metals of the periodic table are minerals. There are exceptions:  The gases: H 2, N 2, O 2, F 2, Cl 2, and the Noble Gases  The metal Mercury (Hg) and the non-metal Bromine (Br 2 ) Hg Br 2

What is a Mineral?  Minerals have definite chemical compositions.  Minerals are pure substances meaning they are either compounds, or elements.  Minerals are never mixtures Native Copper

What is a Mineral?  Minerals have well defined crystal structures.

Classification of Minerals Minerals are classified according to the following criteria: Minerals are classified according to the following criteria:  Chemical Composition (eight classes)  Crystal System (six systems)  Method of Formation (three methods)

Chemical Composition Native ElementsNative Elements SilicatesSilicates CarbonatesCarbonates HalidesHalides OxidesOxides HydroxidesHydroxides SulfidesSulfides SulfatesSulfates

Chemical Composition: Native Elements  Elements that can be found in a pure state  Common native elements include gold, silver, and copper and copper Gold (Au) Copper (Cu)

Chemical Composition: Silicates  The largest chemical class of minerals.  Silicates are so prevalent because the silicate structure comes in many forms.  These forms include: individual tetrahedra, single chains, double chains, sheets, and network solids  Common minerals include: Olivine, Orthoclase and plagioclase Feldspars, and Quartz Silica Tetrahedron Single Chain Double Chain Sheet / Network Solids

Chemical Composition: Carbonates  Carbonates include all minerals that include the CO 3 -2 anion.  Common carbonates include Calcite (CaCO 3 ) and Dolomite (MgCO 3 )  Calcite is the mineral that comprises limestone

Chemical Composition: Halides  Halides are minerals that contain anions from the halogen (Gr. “Salt Forming”) family of the periodic table.  Halides will have F -, Cl -, Br -, I -, anions as part of their chemical composition  Among the most common halides are halite (NaCl) and Fluorite (CaF 2 )

Chemical Composition: Oxides and Hydroxides  Oxides include all minerals that contain the O -2 anion.  Hydroxides contain the OH - anion  Common Oxides include Hematite and Magnetite (both are iron oxides)

Chemical Composition: Sulfides  Sulfides include all minerals that contain the S -2 anion  Common Sulfides include Galena (PbS) and Pyrite (FeS)

Chemical Composition: Sulfates  Sulfates include all minerals that include the SO 4 -2 polyatomic anion.  Common sulfates include Gypsum (CaSO 4 ) and Epsomite (MgSO 4 )

Crystal Systems  Cubic  Tetragonal  Orthorhombic  Hexagonal  Monoclinic  Triclinic

Crystal System: Cubic or Isometric

Crystal System: Tetragonal

Crystal System: Orthorhombic

Crystal System: Hexagonal

Crystal System: Monoclinic

Crystal System: Triclinic

Methods of Formation  Igneous  Metamorphic  Chemical

Method of Formation: Igneous Minerals Igneous minerals are those minerals which form from the cooling and solidification of magmas (inside the Earth) and lavas (on the surface of the Earth). Quartz MicaFeldspar Olivine

Method of Formation: Metamorphic Minerals Metamorphic minerals are those that form from pre-existing minerals that have been exposed to high temperature and or pressure. Metamorphic minerals are those that form from pre-existing minerals that have been exposed to high temperature and or pressure. Staurolite DioptaseGrossularSpessartite

Chemical Formation: Evaporites Evaporite minerals form as the water that Evaporite minerals form as the water that minerals are dissolved in evaporates. minerals are dissolved in evaporates. Evaporation increases the concentration of a Evaporation increases the concentration of a mineral until the solution is saturated. mineral until the solution is saturated. Any further evaporation will result in the Any further evaporation will result in the formation of mineral crystals. formation of mineral crystals. Halite – NaCl The blue is the result of trace elements

Chemical Formation: Precipitates Precipitate minerals form when the concentration of ions in solution increases to the point that insoluble salts form and sink to the bottom of the body of water in which it forms. Precipitate minerals form when the concentration of ions in solution increases to the point that insoluble salts form and sink to the bottom of the body of water in which it forms. Precipitates often form in lagoons and in lakes that dry out due to rapid evaporation, or when calcium rich fresh water pours into ocean water with a significant amount of dissolved CO 2 Precipitates often form in lagoons and in lakes that dry out due to rapid evaporation, or when calcium rich fresh water pours into ocean water with a significant amount of dissolved CO 2 Calcite – CaCO 3 Dolomite – CaMg(CO 3 ) 2

How are Minerals Identified? Minerals are identified using several physical properties. Among the physical properties used are: Minerals are identified using several physical properties. Among the physical properties used are: Color Cleavage Hardness Fracture Streak Unique - Properties Luster Luster

Color  Color is the least useful of all identifiable characteristics of minerals  The same mineral may come in many color varieties due to the presence of trace elements. Ex. quartz quartz  Many different minerals may appear to be the same color Ex. gold and pyrite gold and pyritegold and pyrite

Hardness  Hardness is the resistance that a mineral has to being scratched by another mineral.  Mohs Scale of Hardness is used to determine the hardness of a mineral sample Mohs Scale of Hardness Mohs Scale of Hardness

Streak  Streak is the determination of the true color of a mineral by looking at a powdered sample of the mineral.  Minerals are powdered by rubbing them against a piece of unglazed porcelain plate.  Powdering the mineral eliminates the influence of trace elements  This is most useful for minerals softer than Mohs 7

Luster  Luster is the quality of the light reflected from the surface of a mineral.  There are over thirty categories of luster and it takes an expert to differentiate them all  In this course we will only classify minerals as having a metallic, non-metallic, or glassy luster.

Cleavage  Cleavage occurs when minerals split along flat, smooth surfaces.  Cleavage occurs because there is a plane of weakness created by weak molecular bonds oriented in a particular direction  There are six types of cleavage each associated with the number of planes involved and the angle between the cleavage planes

Fracture  Fracture of mineral samples occurs when minerals break along uneven, or jagged surfaces.  Fracture occurs when there is no particular orientation to the weak bonds in a mineral, or when all bonds are of equal strength  There are six types of fracture

Special Properties  Magnetism ex. magnetite  Taste ex. halite  Oder ex. sulfur and pyrite  Phosphorescence ex. calcite  Fluorescence ex. calcite  Specific Gravity ex. all minerals  Reaction with Acids/Bases ex. calcite  Birefringence ex. calcite

Uses of Minerals The two primary uses of minerals are: Commercially and Strategically Valuable Ores Valuable OresGemstones

What is an Ore?  An ore is a mineral that can be mined and refined to extract a commercially or strategically valuable substance  Examples of important ores are:  hematite and magnetite (iron ores)  galena (lead ore)  sphalerite (zinc ore)  bauxite (aluminum ore)

Gemstones  To qualify as a gemstone a mineral must be:  Rare – increases monetary value  Durable – increases longevity  Beautiful – increases demand

Varieties of Quartz Varieties of Quartz

Different Minerals with the Same Color Different Minerals with the Same Color

Mohs Scale of Hardness Mohs Scale of Hardness