Minerals Chapter 8

Minerals "A mineral is an element of chemical compound that is normally crystalline and that has been formed as a result of geological processes" (Nickel, E. H., 1995). Minerals are naturally-occurring inorganic solid that has a specific chemical composition and crystal structure

Minerals 2500 Different Minerals 100 Considered Common Minerals Fewer than 20 (most common) – considered rock forming minerals

Eight elements make up 98% percent of Earth’s Crust Oxygen 46.6 % Silicon 27.7 % Aluminum 8.1 % Iron 5.0 % Calcium 3.6 % Sodium 2.8 % Potassium 2.6 % Magnesium 2.1 % Others 1.5 %

Mineralogist A scientist who studies minerals including rock- forming minerals

Characteristics of Minerals Occurs naturally in the Earth Inorganic-not formed from living or once living things Solid Specific chemical composition Atoms arranged in a definite repeating pattern

Minerals Crystals are a solid that have regular shape and flat sides called faces A Geode is a hollow rock that is lined with crystals.

Crystal Shapes Tetragonal

Crystal Shapes Cubic

Crystal Shapes Hexagonal

Crystal Shapes Orthorhombic

Crystal Shape Monoclinic

Crystal Shape Triclinic

Uses of Minerals

Ores Minerals from which metals and nonmetals can be removed in usable amounts Gold

Malleability The ability of a substance to be hammered into thin sheets without breaking

Ductility Ability of a substance to be pulled into thin strands without breaking

Smelting Process during which ore is heated in such a way that metal can be separated from it

Gems Gems are 1) Rare2) Durable 3) Beautiful

Precious Stones Rarest and most valuable

Semi-Precious Stones Not as Rare and Valuable Hardness of less than 7 Opal Garnet

Mineral Identification Minerals can be identified by their color and texture Beryl-Emeralds

Color Easily observed, however many minerals come in a variety of colors and some are colorless; in addition, the color of minerals can change as a result of exposure to or treatment with heat, cold, pollution or radiation

Texture The way a mineral feels.(greasy, earthy, etc. Talc

Luster Describes the way the mineral reflects light from its surface Two types-Metallic and Non-metallic

Metallic Luster Chalcopyrite Metallic Luster

Nonmetallic Luster Kaolinite Non-Metallic Luster

Vitreous Vitreous-Glassy Tourmaline

Pearly Looks like the shiny quality of pearls

Greasy Sun tan oil look Graphite

Silky Shines like silk Schorl

Adamantine Brilliant, like a cut diamond The Hope Diamond

Hardness Mineral’s ability to resist being scratched

Mohs Hardness Scale Talc1 Gypsum2 Calcite3 Fluorite4 Apatite5 Feldspar6 Quartz7 Topaz8 Corundum9 Diamond10

Field Hardness Test 1Easily scratched by fingernail 2Scratched by fingernail 3Easily scratched by a house nail; Will not scratch a copper penny 4Easily scratched by nail 5Difficult to scratch with nail; Will not scratch glass

Field Hardness Test (cont.) 6.May barely scratch glass; will not scratch steel file 7.May barely scratch steel file Will scratch glass Easily scratches a steel file

Streak Color of the powder scraped off a mineral when it is rubbed against a streak plate Streak Plate-an unglazed piece of porcelain

Density Mass per Unit Volume

Specific Gravity Ratio between the Mass of a mineral and the Mass of an equal volume of water

Cleavage Occurs when a mineral splits along smooth, definite surfaces Calcite Cleavage

Fracture Conchoidal Fracture-Curved Like a Rainbow

Fracture Hackly Fracture- Uneven, like broken glass Anhydrite

Fracture Splintery or Fibrous Fracture- Breaks into fibers

Special Properties Double Refraction- Causes a beam of light to be split in two, producing a double image Calcite

Special Properties Magnetism-Acts like a weak magnet Magnetite

Special Properties Fluorescence- Mineral glows under UV light

Special Properties Phosphorescence- Release of visible light, resulting from the absorption of UV light

Special Properties Radioactivity- Release of energy by certain elements due to the decay of an atom into a lighter nucleus Uraninite Metatorbernite

Mineral Groups Silicates-Made of Oxygen and Silicon-Orthoclase Sulfates-Made of Oxygen and Sulfur- Barite Oxides-Made of oxygen and usually a Metal-Hematite Halides-Made of Chlorine or Fluorine and Sodium, Potassium, or Calcium Carbonates-Made of Carbon and Oxygen-Dolomite Halite

Mineral Examples Azurite Graphite Malachite Sulfur Sapphire