Earth Science Notes MINERALS

Definition of a Mineral A mineral is a naturally occurring, inorganic, homogeneous solid with a definite chemical composition and an ordered atomic arrangement. A mineral is a naturally occurring, inorganic, homogeneous solid with a definite chemical composition and an ordered atomic arrangement.

Five parts to this definition Naturally occurring – not man made, may be found on earth, space, or other planets. Naturally occurring – not man made, may be found on earth, space, or other planets. Inorganic – minerals are not formed by living things but by earth processes. Inorganic – minerals are not formed by living things but by earth processes.

Five parts to this definition Homogeneous solid – made up with the same atoms throughout the mineral. Homogeneous solid – made up with the same atoms throughout the mineral. The Mineral Halite (Sodium Chloride)

Five parts to this definition Definite chemical composition - atoms must occur in the same ratios. Definite chemical composition - atoms must occur in the same ratios. Most minerals are ionic compounds – recall ionic compounds have a definite ratio of atoms  aluminum oxide  2:3 ratio Most minerals are ionic compounds – recall ionic compounds have a definite ratio of atoms  aluminum oxide  2:3 ratio (2 Aluminum atoms to 3 Oxygen atoms)

Five parts to this definition Ordered atomic arrangement – must be crystalline – have repeating units Ordered atomic arrangement – must be crystalline – have repeating units Unit cell – the most basic component of a crystal. Unit cell – the most basic component of a crystal. Glasses, like obsidian, are not minerals Glasses, like obsidian, are not minerals

Orderly Atomic Arrangement Crystals: solids where atoms are arranged in an orderly repeating pattern. Front View of Crystal LatticeEnlarged 3-D view of Unit Cell

Orderly Atomic Arrangement  Crystal Lattices – repeated unit cells

Orderly Atomic Arrangement Crystal Systems – made up of crystal lattices Types of crystal systems (also see p 64) Types of crystal systems (also see p 64) Cubic Cubic Hexagonal Hexagonal Monoclinic Monoclinic Tetragonal Tetragonal Orthorhombic Orthorhombic Triclinic Triclinic

Orderly Atomic Arrangement Unit Cell  Crystal Lattice  Crystal System

Mineral Formation Minerals form as a result of two processes Magma cooling Minerals formed depend on the elements present and the amount of those elements. Minerals formed depend on the elements present and the amount of those elements. The size of the mineral crystal depends on the rate at which the crystal cooled. The size of the mineral crystal depends on the rate at which the crystal cooled.

Mineral Formation Minerals form as a result of two processes Solutions evaporating Solutions have two parts Solutions have two parts Solute – substance being dissolved Solute – substance being dissolved Solvent – substance doing the dissolving Solvent – substance doing the dissolving With some solutions the solvent (water) can be evaporated and the solute (salt) dissolved reappears in crystal form. With some solutions the solvent (water) can be evaporated and the solute (salt) dissolved reappears in crystal form.

Mineral Formation Solutions evaporating to form minerals: the spotted lake (kliluk), situated in osoyoos, Canada, contains one of the highest concentrations of minerals in the world (mainly epsom salts, calcium and sodium sulphates).

Mineral Classification Most mineral groups are based on the elements that are in the mineral. Most mineral groups are based on the elements that are in the mineral. Silicates – vast majority of the earth’s crust. Silicates – vast majority of the earth’s crust. Ex: Quartz and Feldspar Ex: Quartz and Feldspar Oxides – minerals that have oxygen in them. Oxides – minerals that have oxygen in them. Ex: Hematite and Magnetite Ex: Hematite and Magnetite Sulfides – minerals that have sulfur in them. Sulfides – minerals that have sulfur in them. Ex: Pyrite and galena Ex: Pyrite and galena Halide – … have one of the halogens in them. Halide – … have one of the halogens in them. Ex: halite (NaCl) and Fluorite Ex: halite (NaCl) and Fluorite Pure metal elements: Gold, silver, etc Pure metal elements: Gold, silver, etc

Mineral Identification Physical Properties of minerals allow for accurate identification Hardness Hardness Luster Luster Specific Gravity Specific Gravity Streak Streak Cleavage Cleavage Special Properties Special Properties

Mineral Identification Hardness: determine by Mohs Scale Hardness: determine by Mohs Scale HARDNESS SCALE INDEX MINER AL COMMON OBJECTS 1Talc 2GypsumFingernail 3Calcite 4FluoriteCopper Penny 5Apatite 6Orthoclase 7QuartzGlass 8Topaz 9Corundum 10Diamond

Mineral Identification Luster: reflecting of light Luster: reflecting of light The two main types of luster are metallic and nonmetallic. The two main types of luster are metallic and nonmetallic. Metallic lusterNonmetallic Luster

Mineral Identification Specific Gravity: Specific gravity is the "heaviness" of a mineral. Specific Gravity: Specific gravity is the "heaviness" of a mineral. It is defined as a number that expresses the ratio between the weight of a mineral and the weight of an equal volume of water. Water has a specific gravity of 1. It is defined as a number that expresses the ratio between the weight of a mineral and the weight of an equal volume of water. Water has a specific gravity of 1.

Mineral Identification Streak: is the color of the powder left on a streak plate Streak: is the color of the powder left on a streak plate

Mineral Identification Cleavage: is the ability of a mineral to break along preferred planes. Cleavage: is the ability of a mineral to break along preferred planes. Fracture: tendency of a mineral to break along curved surfaces without a definite shape

Mineral Identification Special Properties of minerals Special Properties of minerals Transparency Transparency Magnetism Magnetism Tenacity (how tough a mineral is) Tenacity (how tough a mineral is)

Minerals Summary Summary What makes something a mineral? What makes something a mineral? Five characteristics Five characteristics Arrangement and organization of crystal structures Arrangement and organization of crystal structures Unit Cell  lattices  Crystal systems Unit Cell  lattices  Crystal systems Formation of Minerals Formation of Minerals From lava / Solutions From lava / Solutions Mineral Identification Mineral Identification Based on physical properties Based on physical properties