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MINERALS

MINERALS. What is a Mineral?. Minerals must have four characteristics: it must be inorganic—not made of or by living things; it must occur naturally—it cannot be man-made; it must be a crystalline solid; it must have a consistent chemical composition. Types of Minerals.

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MINERALS

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  1. MINERALS

  2. What is a Mineral? Minerals must have four characteristics: • it must be inorganic—not made of or by living things; • it must occur naturally—it cannot be man-made; • it must be a crystalline solid; • it must have a consistent chemical composition.

  3. Types of Minerals • 10 are so common that they make up 90% of Earth’s crust. • quartz, orthoclase, plagioclase, muscovite, biotite, calcite, dolomite, halite, gypsum, and ferromagnesian minerals. • Two main groups: • silicate minerals • nonsilicate minerals

  4. Silicate Minerals • Contain silicon and oxygen, and possibly one or more metals • Common silicate minerals • quartz, feldspars, micas ,and ferromagnesian minerals, such as amphiboles, pyroxenes, and olivines. • Make up 96% of Earth’s crust. • Quartz and feldspar alone make up more than 50% of the crust.

  5. Nonsilicate Minerals • No silicon and oxygen compounds • Make up about 4% of Earth’s crust. • Six major groups based on their chemical compositions • carbonates, halides, native elements, oxides, sulfates, and sulfides.

  6. Mineral Structure • Each type of mineral is characterized by a specific geometric arrangement of atoms, or its crystalline structure. • A crystal isa solid whose atoms, ions, or molecules are arranged in a regular, repeating pattern

  7. Silicate Structure • Silicon-Oxygen Tetrahedron- basic unit of the structure of silicate minerals. Si+4 and 4 O-2 • Ex: Olivine • Ex: Beryl and tourmaline

  8. Silicate Structure • Ex: Pyroxenes • Ex: Amphiboles

  9. Silicate Structure • Ex: Biotite and muscovite

  10. Silicate Structure • Ex: Quartz and feldspar

  11. Nonsilicate Structure • Diverse chemical compositions = vast variety of crystalline structures. • Common nonsilicate mineral structures: • cubes, hexagonal prisms, and irregular masses.

  12. Mineral Identification • Mineralogist- a person who examines, analyzes, and classifies minerals • Chemical composition and crystalline structure determine a minerals properties • Many of these properties can be used to identify a mineral sample.

  13. Mineral Properties Color • Easily observed but unreliable for mineral identification. • Can be affected by impurities or weathering. Streak • Color of a mineral in powdered form • Streak is more reliable than color for the identification of minerals.

  14. Mineral Properties Luster • The way a mineral reflects light • Metallic luster- reflects light like polished metals. • Nonmetallic luster- duller appearance • glassy, waxy, pearly, brilliant, and earthy.

  15. Mineral Properties

  16. Mineral Properties • Cleavage- tendency of a mineral to split along specific planes to form smooth, flat surfaces Cleavage and Fracture

  17. Mineral Properties Types of Cleavage Muscovite Halite Feldspar

  18. Mineral Properties • Fracture- breaks along curved or irregular surfaces • Uneven or irregular fractures • Splintery or fibrous fractures • Conchoidal fractures Cleavage and Fracture

  19. Mineral Properties Hardness • Ability of minerals to resist scratching. • Does NOT mean “resistance to cleavage or fracture.” • Determined by comparing to minerals • Mohs hardness scale the standard scale for the hardness of minerals. • The strength of the bonds between the atoms of amineral determines its hardness.

  20. Mineral Properties

  21. Mineral Properties Crystal Shape • Certain minerals always have the same general shape because the atoms that form the mineral’s crystals always combine in the same geometric pattern. • The six basic crystal systems: • isometric or cubic, orthorhombic, tetragonal, hexagonal, monoclinic, and triclinic

  22. Mineral Properties

  23. Mineral Properties Density • density the ratio of the mass of a substance to the volume of a substance • The density of a mineral depends on the kinds of atoms in the mineral and on how closely the atoms are packed. density = mass volume

  24. Special Properties of Minerals Fluorescence and Phosphorescence • The ability to glow under UV light is called fluorescence. • The property of some minerals to glow after the ultraviolet light is turned off is called phosphorescence.

  25. Special Properties of Minerals Chatoyancy and Asterism • Light is reflected causing a silky appearance that is called chatoyancy • Tiger’s Eye • A similar light reflecting effect called asterism is when a six-sided star appears • Star Sapphire

  26. Special Properties of Minerals Double Refraction • Producing a double image of objects viewed through the mineral.

  27. Special Properties of Minerals Magnetism • Are attracted to magnets or may be magnetic themselves. • In general, nonsilicate minerals that contain iron are more likely to be magnetic than silicate minerals are.

  28. Special Properties of Minerals Radioactivity • The property known as radioactivity results as unstable nuclei decay over time into stable nuclei by releasing particles and energy. • A Geiger counter is used to detect the released particles and, thus, to identify minerals that are radioactive.

  29. Value of Minerals

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