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Minerals & Rocks

Minerals & Rocks. Honors Notes. A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and a crystalline structure . . Lets put that in a list format:. 1. Minerals are a naturally occurring substance. 2. Minerals are solids.

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Minerals & Rocks

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  1. Minerals & Rocks Honors Notes

  2. A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and acrystalline structure.

  3. Lets put that in a list format: 1. Minerals are a naturally occurring substance. 2. Minerals are solids. 3. Minerals have a definite chemical composition. • 4. The atoms that make up minerals are arranged in an orderly pattern (They form crystals). • 5. Minerals are inorganic. (They were never alive.)

  4. Silicate Minerals • Contain silicon (Si) plus oxygen (O) or silicon dioxide (SiO2). • The most common rock-forming minerals • May contain one or more other elements with the silicon and oxygen. • EX: Feldspars are formed depending on what else combines with the silicon and oxygen. • Orthoclase- Si, O, K, AL • Plagioclase- Si, O, Ca, Na • EX: Quartz composed of only Si and O • Make up 96% of the Earth’s crust. • Earth’s oceanic crust is denser and contains a larger percentage of silicates than continental crust. Two Major Types of Minerals

  5. Biotite Quartz Muscovite Silicate Minerals Plagioclase Feldspar

  6. Non-silicates • Contain no silicon • Many important mineral groups are not silicates. • Non-Silicate Minerals include: carbonates, (limestone, marble) oxides (hematite), halides (halite/rock salt), sulfides (pyrite), sulfates (gypsum), and native metals (gold, silver, copper). • The non-silicate groups are a source of many valuable ore minerals and building materials. • To be an ore, a mineral must occur in large enough quantities to be economically recoverable. Two Major Types of Minerals (cont’d)

  7. Pyrite Hematite Non-Silicate Minerals Halite (salt)

  8. Gold Non-Silicate Minerals Flourite Galena

  9. Mineral appearance • Hardness • Luster • Specific gravity • Streak • Cleavage andfracture Physical Properties

  10. How it looks like • What color is it? • Which one of the following is gold? Identify by appearance. Mineral appearance

  11. A measure of how easily a mineral can be scratched • MohsHardness Scale • developed in 1812 by FriedrickMohs (an Austrian mineral expert) as a method to identify minerals. Hardness

  12. The way a mineral reflects a light. • Either metallic or nonmetallic Luster

  13. 19 times heavier • The specific gravity of a mineral is the ratio of its weight compared with the weight of an equal volume of water. • Gold has specific gravity of 19 • It means gold is 19 times heavier than water. Specific Gravity

  14. Specific gravity

  15. When a mineral is rubbed across a piece of porcelain tile a streak of powdered mineral is left behind. Streak

  16. Cleavage is the way that mineral breaks. • Minerals that break along smooth, flat surfaces have cleavage. • Mica has cleavage Cleavage

  17. quartz • Mineral that breaks uneven, rough, or jagged surfaces have fracture. • Quartz has fracture and Fracture!...

  18. Some physical properties are controlled by the orderly arrangement of atoms in a mineral’s structure. • The arrangement of atoms and the bonds between them can reflect the way a mineral breaks, how hard it is, and what types of crystal shape it has. Atom Arrangement

  19. Crystal Shape – Types of Symmetry Which of these would halite be the shape of?

  20. Name Plane =Basal 1 =Prismatic 2 3 =Cubic =Rhombo- hedral 3

  21. An illustration appearance:luster,color and streak

  22. An illustration cleavage and fracture

  23. CLEAVAGE FRACTURE Identify the minerals below for cleavage and fracture

  24. Magnetic – use a magnet and see if it sticks • Taste – certain minerals have a specific taste • Fluorescence – glowing while under a U.V. light • Phosphorescent – continues to glow after the U.V. light is off • Radioactive – test minerals with a Geiger counter • Double Refraction – Splits light rays into 2 parts. (see a double image) Look through the mineral for the image. Special Properties of Minerals

  25. A rock is a naturally formed consolidated solid mixture made up of minerals, rock fragments, or volcanic glass • Essential Minerals: always occur in the rock • Accessory Minerals: sometimes occur in rock Rocks

  26. Igneous • - Made up of magma or lava when it cools and hardens • Sedimentary • - Made from sediments • Metamorphic • - Rocks changed by pressure & heat Classify Rocks by how they form

  27. Formed from lava or magma • Lava : extrusive or volcanic • Magma: Intrusive or plutonic (pillow-like) • Intrusive Igneous rocks • Formed from magma which cools and solidifies below Earth’s surface • Cooling and solidification take a long time resulting in large visible crystals (coarse-grained) • Extrusive Igneous Rocks • Small to no mineral crystals due to faster cooling lava above Earth’s surface (fine-grained) • Occurs at volcanoes or through ocean floor Igneous Rocks

  28. Rock is a fused mixture of minerals. Some of these minerals could be in bits and pieces of other rocks. • Broken into pieces (clasts) through weathering • Rock exposed at the surface is attacked by the weather • Water: enters cracks, expands, & breaks rocks down • Rain: acidic dissolves minerals • Movement in rivers: collects at the bottom Sedimentary Rocks

  29. Build very slowly in layers, until the environment changes • Compaction: pieces compact due to weight squeezing them together • Cementation: minerals acting as cement holding sediments together • Precipitation: water evaporates & minerals are left behind Sedimentary Rocks Formation

  30. Classifying Sedimentary RocksClastic Rocks: pieces of other rocks

  31. Minerals in water which evaporates to leave behind deposits (rocks) or fossil materials that compact into rock. • Ex: • 1. Limestone: calcite and seashells • 2. Rock salt: halite • 3. Rock gypsum: gypsum • 4. Chert: Quartz • 5. Coal: fossil materials NonClastic Rocks

  32. Form from pre-existing igneous, sedimentary, or metamorphic rocks, as a result of temperature and pressure changes • 3 types of changes: • Rearrangement of mineral grains • Enlargement of crystals • Change in chemistry of rock Metamorphic Rocks

  33. Foliation: Foliated textures in metamorphic rocks have lots of layers or bands. • Non-Foliated: metamorphic textures include rocks whose grains are in more random orientations. (no bands) • Tend to have random crystal orientation and uniform grain size. • Mineral grains tend to grow larger as metamorphism increases. Characteristics of Metamorphic Rocks

  34. Foliation Nonfoliated Characteristics of Metamorphic Rocks

  35. Igneous • crystals intersecting at angles • size of the grain • Sedimentary • layers of rock pieces • Metamorphic • pressure created results in lines • pressure and heat create grains in foliation (wavy patterns) • hardest of the 3 rocks Hints for Identifying Rocks

  36. Changes of rocks from one rock type to another Magma melting cooling Metamorphic Rock Igneous Rock weathering heat & pressure Rock Cycle Sediments Sedimentary Rock cementation or compaction

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