MINERALS

1. MINERALS Chapter 4

2. What is a Mineral? Characteristics of a Mineral: • Naturally occurring • Formed by natural processes • Inorganic • Not living – never will be • Solid with specific chemical composition • Definite shape & volume (NOT LIQUID OR GAS) • Have a formula (chemical composition) unique to it • Definite crystalline structure • Atoms are arranged in a regular geometric pattern that is repeated over and over again

3. There are about 3000 minerals found in the Earth’s crust, but only 30 are common. Of those 30, the most common are called rock-forming minerals.Since elements are also found in the Earth’s crust, approximately 90, the vast majority of minerals are made up of the eight most common elements in the Earth’s crust. 1. Oxygen 2. Silicon 3. Aluminum 4. Iron 5. Calcium 6. Sodium 7. Magnesium 8. Potassium

4. How are Minerals Formed? Minerals are formed in three ways: Cooling Magma – Magma is molten (melted) material found beneath the Earth’s surface. As it cools, it forms crystals that then form minerals (the longer they cool, the larger the crystals!) Water can only dissolve so much solid in a solution. Once it reaches that point, all other solids precipitate (fall to bottom). What precipitates are crystals – thus minerals. When elements DO dissolve in solution, if liquid evaporates, solid crystals remain. Crystals = Minerals.

5. Silicates Largest group of rock-forming minerals. All Silicates contain Oxygen (O) and Silicon (Si) Si and O are the two MOST ABUNDANT elements in the Earth’s crust and make up 96% of the Earth’s crust Examples include Feldspar and Quartz

6. Carbonates Contains CO3 with metallic elements Some have distinctive coloration Examples include calcite and dolomite Found in limestone, coquina, and marble

7. Oxides Compounds of oxygen and a metal Examples include Hematite and Magnetite Source of iron and uranium

8. Identifying Minerals Ways to Identify Minerals: • Color • Trace elements will give off a specific color • Luster • The way a mineral reflects light • Either metallic (shiny) or nonmetallic (dull) • Texture • How the mineral feels to the touch (smooth, rough, greasy, soapy) • Streak • The color of a mineral when broken and powdered on a porcelain streak plate

9. Hardness • How easily a mineral can be scratched • “Rate” on Moh’s Hardness Scale, which ranges from 1-10 • Cleavage & Fracture • Cleavage – when a mineral splits evenly along one or more flat planes • Fracture – when minerals break along rough or jagged edges • Density & Specific Gravity • Differences in weight are due to differences in density (mass per unit of volume) • Reflects the atomic weight and structure, NOT THE SIZE OR SHAPE

10. MINERAL USES ORES A mineral that contains a useful substance and can be mined for profit Most ores are obtained through open-pit mining Examples – Iron, Aluminum, Hematite, Aluminum, Rutile (contains titanium… sports equipment!) GEMS Valuable minerals prized for their rarity and beauty Examples – Ruby, Emeralds, Diamonds

11. IGNEOUS ROCKS Chapter 5

12. What are Igneous Rocks? Igneous Rocks form from the Cooling and crystallization of magma Igneous is Latin for “fire” Most igneous rocks are associated with fiery lava flows (Lava is simply magma that flows onto the surface of the Earth).

13. Magma is formed from the heat and pressure from inside the Earth. Magma is made up of molten rock, gases, and minerals. The amount of silica determines the melting temperature and how quickly magma flows.

14. How Igneous Rocks Melt and Form Rocks melt in different ways, based on their compositionThis explains why magma is a mixture of crystals and molten rock Partial Melting Fractional Crystallization The process where some minerals melt at low temperatures while others remain solid As the water content of a rock increases, the melting point decreases The process where different minerals solidify at different temperatures

15. Classifying Igneous Rocks Igneous rocks are classified according to three main things: 1. mineral compositions 2. Grain size 3. Texture

16. Grain Size Varies depending on the amount of time lava/magma takes to cool Extrusive Igneous Rocks Outside of Earth, lava cools quickly and produces little to no visible crystals (Fine) Intrusive Igneous Rocks Inside of Earth, magma cools slowly and produces large crystals (Coarse)

17. Texture As grains crystallize from magma, they grow together and form irregular edges. Although this is characteristic of many igneous rocks, well-shaped crystals can also form under certain conditions. Many rocks have porphyritic texture, which is characterized by large, well-formed crystals surrounded by finer-grained crystals of the same or different material.

18. Chapter 6 Sedimentary rocks

19. Sedimentary Rocks come from sediments, which are pieces of solid material deposited by wind, water, ice, etc. Sediments cover most of the Earth’s surface. When sediments become cemented and compact together, they form Sedimentary Rocks. The formation of Sedimentary Rocks begins when weathering and erosion produce sediments. Where do Sedimentary Rocks come from?

20. Weathering: processes that break rock into smaller pieces • Chemical Weathering – occurs when the minerals in a rock are dissolved or otherwise chemically changed • Physical Weathering – rocks break into smaller grains (clastic sediments) and remain chemically unchanged • Erosion: removal and movement of sediments • By wind, water, gravity, glaciers • Deposition – when sediments are laid down (largest at bottom and smallest at top) • Burial • Lithification: processes that transform sediments into rock • Compaction – weight of overlying sediments forces the sediment grains closer together, causing physical changes • Cementation – occurs when mineral growth cements sediment grains together into solid rock Formation of Sedimentary Rocks

21. Features of sedimentary rocks The primary feature of sedimentary rocks is bedding, or horizontal layering. Bedding can range in size, dependent upon the method of transport. Fossils are the best known features of sedimentary rocks. Fossils show evidence of past life. Sedimentary rocks, unlike other rocks, can be used to determine the type of animals that lived when the rock was formed.

22. There are three main types of sedimentary rocks: • Clastic Sedimentary Rocks • Most common, resulting from lithification of clastic sediments • Formed from the abundant deposits of loose sediments found on Earth’s surface • Classified according to their particle size • Chemical Sedimentary Rocks • Form from evaporation – evaporites • Most commonly form in arid regions, in oceans and drainage basins on continents with low water flow • Organic Sedimentary Rocks • Form from remains of living organisms Types of sedimentary rocks

23. METAMORPHIC ROCKS Chapter 6

24. What are Metamorphic Rocks? • The word metamorphism is derived from the Greek words “meta” (change) and “morphe” (form) • During metamorphism, a rock changes form while remaining solid • So, a metamorphic rock is one that is formed when high temperature and pressure changes a rock without melting it • A rock can change texture, mineralogy, or chemical composition

25. How does a Rock undergo Metamorphism? • The intense heat required for metamorphism ultimately come from the Earth’s internal heat, either through deep burial or nearby igneous intrusions. • The high pressures required for metamorphism can be generated in two ways: • From vertical pressure caused by the weight of overlying rock • From the comprehensive forces generated as rocks are deformed during mountain building

26. Two Types of Metamorphism Regional Metamorphism High temperatures and pressures affect large regions of Earth’s crust Contact Metamorphism Caused when molten rock comes in contact with solid rock

27. Metamorphic Textures Metamorphic Rocks are classified into textured groups. Foliated – wavy layers and bands of minerals Nonfoliated – lack mineral grains with long axes in one direction