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Earth Science Notes

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. Five parts to this definition .

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Earth Science Notes

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  1. Earth Science Notes MINERALS

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

  3. Five parts to this definition • 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.

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

  5. Five parts to this definition • 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 (2 Aluminum atoms to 3 Oxygen atoms)

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

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

  8. Orderly Atomic Arrangement • Crystal Lattices – repeated unit cells

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

  10. Orderly Atomic Arrangement Unit Cell  Crystal Lattice  Crystal System

  11. 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. • The size of the mineral crystal depends on the rate at which the crystal cooled.

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

  13. 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).

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

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

  16. Mineral Identification • Hardness: determine by Mohs Scale

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

  18. Mineral Identification • 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.

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

  20. Mineral Identification • 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

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

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

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