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Rocks and Minerals

Royce Tee David Gozali Edsel Uy

I. Rocks

A. What is a Rock?

B. 3 Kinds of Rocks 1. Igneous Rock ---i. Definition of Igneous Rock- when magma or lava cools and hardens. ---ii. 2 Types of Igneous Rocks --a. Volcanic or Extrusive Rocks - lava cools and crystallizes on the surface of the earth --b. Plutonic or Intrusive - magma crystallizes at depth in the Earth. (it hasn't come out out of the volcano) ---iii. Examples: Basalt, Obsidian and Pumice 2. Sedimentary Rocks ---i. Definition of Sedimentary Rocks - formed from weathering, erosion, deposition, compaction, and cementation that pile up on top of each other. ---ii. 3 types of Sedimentary Rock --a. Clastic Rocks - formed by sediments also know as the "true sedimentary rock" and is made of sediments from other rocks, pebbles, stones, or anything broken off from another rock --b. Conglomerate - also a Clastic Rock. They are Organic Rocks form from the sediments of dead orgainsms like worms, fishes, etc) --c. Chemical Rock - form from solutions that are made from chemicals ---iii. Examples: Sandstone. Siltstone and shale 3. Metamorphic Rocks ---i. Definition of a Metamorphic Rock- rocks that have been changed through metamorphism usually under the Earth. ---ii. 2 Types of Metamorphic Rock --a.Foliated- it has a distinct planar texture (the mineral grains are aligned) --b.Non-foliated- it is formed by regional metamorphism of monomineralic rocks or contact metamorphism ---iii. Examples: Slate, Marble and Greenstone

C. Rock Cycle - the dynamic transitions among igneous, metamorphic and sedimentary rocks. - each type of rock is destroyed and forced out of its balanced condition. -possible factors: a. exposed to atmosphere b. melt as it is subducted under a continent

i. Transition to Igneous -There are two ways when igneous rocks are created. -The two ways are Intrusive and Extrusive. -Intrusive: 1. Rocks are pushed under the Earth's surface. 2. Rocks melt into magma. 3. If the magma can not stay in its liquid state, it will solidify. 4. The magma will cool and solidify into an igneous rock. (rocks that cool within the Earth is called intrusive or plutonic. These rocks have a coarse-grained texture) -Extrusive: 1. Volcanic activity occurs. 2. Magma will cool very rapidly while it is exposed to the atmosphere on the Earth's surface. (Magma: still under the Earth's surface, Lava: has already reached the Earth's surface) 3. Fine-grained and sometimes no crystals can form since it cools so rapidly.

ii. Transition to Metamorphic -Rocks that are exposed to high temperatures or pressures can be physically or chemically changed to metamorphic rock. -Regional metamorphism means the physical or chemical changes to a large mass of rocks over a wide area. - Metamorphic rocks mostly shows distinct bands of differing mineralogy and colors. -Contact metamorphism is caused when a body of rock contacts an igneous intrusion that heats up its surrounding.

ii. Transition to Sedimentary -Weathering and erosion are two main factors of this transition. -These two factors break down the original rocks into smaller fragments. -Dissolved material in the smaller fragments are carried away. -The fragments are accumulated and buried by additional material. -A rock made of the fragments and grains is fused together. (This is called lithification)

II. Minerals

A. What is a Mineral? 1. Is naturally occurring - Formed by geological processes - Laboratory created gems such as synthetic diamonds and rubies don't count 2. Is a solid within the normal temperature ranges of the earth’s surface 3. Is inorganic (mostly) 4. Has a fixed chemical formula - Example: each molecule of salt will always have one sodium atom and one chlorine atom 5. Has an orderly crystalline structure - Atoms and ions that make up a mineral are arranged in an orderly and repetitive manner

B. Mineral Properties

1. Color - In opaque minerals, their color tends to be more consistent (usually having the same color) - However, in transparent and translucent minerals have a much more varied degree of color because of trace minerals in them which does not make color alone a good way of identifying a mineral 2. Streak - The color of the mineral in powdered form - Shows the true color of the mineral because in large solid form, trace minerals can change the color appearance of a mineral by reflecting the light in a certain way - Because of this, streak is a much more reliable way of identifying minerals than color 3. Hardness - Measure of the mineral's resistance to scratching - Can be measured using the Moh's scale:


 * Mineral || Hardness Level ||
 * Talc || 1 ||
 * Gypsum || 2 ||
 * Calcite || 3 ||
 * Fluorite || 4 ||
 * Apatite || 5 ||
 * Orthoclase Feldspar || 6 ||
 * Quartz || 7 ||
 * Topaz || 8 ||
 * Corundum || 9 ||
 * Diamond || 10 ||

4. Cleavage - How easily the mineral breaks when hit sharply 5. Fracture - The quality of the cleavage surface 6. Crystalline Structure - The shape of the crystals in the mineral determined by the arrangement of atoms, molecules, and ions. 7. Diaphaneity (Amount of Transparency) - How easily light passes through 8. Tenacity - How the particles of a mineral hold together or resist separation 9. Magnetism - How the mineral attracts or repels a magnet 10. Luster - How a mineral reflects light - Usually metallic minerals reflect light, and non-metals don't 11. Odor - Most minerals have no odor unless they are acted upon in one of the following ways: moistened, heated, breathed upon, or rubbed 12. Taste - Only soluble minerals (such as salt) should be tasted, so it's not the best way to determine a mineral 13. Specific Gravity - A comparison or ratio of the weight of the mineral to the weight of an equal amount of water

C. Classification of Minerals (Dana System) 1. Native Elements - Most minerals are compounds, but in this category the minerals are composed of only one element in a naturally pure form (meaning that no other element was mixed into the mineral) 2. Silicates - Largest group of minerals - Made from metals combined with silicon and oxygen 3. Oxides - A combination of a metal with oxygen 4. Sulfides - Made of compounds of sulfur usually with a metal - Mostly heavy and brittle 5. Sulfates - Compounds of sulfur combined with metal and oxygen - Mostly soft and translucent 6. Halides - F ormed from halogen elements like chlorine, bromine, fluorine, and iodine combined with metallic elements - Soft and easily dissolve in water 7. Carbonates - Group of minerals made of carbon, oxygen, and a metallic element 8. Phosphates - Not as common in occurrence as the other families of minerals - Formed by weathering of other minerals 9. Mineraloid - Other substances that do not fit under any of the other eight classes - Examples are opal (non-crystal structure), jet (organic origin, non-crystal), amber (organic, non-crystal), and pearl (organic origin) III. Sources: - http://en.wikipedia.org - http://www.rocksandminerals4u.com/index.html - http://www.tulane.edu/~sanelson/geol111/igneous.htm - http://webmineral.com/ - http://geology.about.com/cs/basics_roxmin/a/aa011804b.htm - http://geology.csupomona.edu/drjessey/class/Gsc101/Meta.html - http://rst.gsfc.nasa.gov/Sect2/rock_cycle_800x609.jpg

IV. Check-up quiz

1. What two factors contribute to the creation of metamorphic rocks? 2. What do you call the process of the fusing of fragments to turn into a sedimentary rock? 3. Differentiate intrusive and extrusive formation of igneous rocks. 4. Differentiate Clastic and Conglomerate sedimentary rocks. 5. Which group of minerals is composed of oxygen, carbon and a metal? 6. Why can't mineraloids be classified under the other groups of minerals? 7. Which group of minerals is the biggest? 8. What do scientists use to determine the hardness of a material? 9. Why can't we say that laboratory created gems are minerals? 10. Why is streak a better way of determining a mineral than color?

V. Mining (Issue):

1. Mining is the extraction of minerals from the earth. 2. Bad environmental effects: - could lead to erosion, formation of sinkholes, and loss of biodiversity - results to waste such as harmful chemicals, which is simply dumped into the rivers, soil, etc. - could also lead to denudation of forests (example: in surface mining for coal, the top layer of the ground is stripped away to get to the coal beneath, but this results in stripping large amounts of land) - also, since minerals are non-renewable, this depletes the minerals in the earth until one day there might not be any left 3. Other negative effects - in addition to the environmental effects, there are also many mining-related deaths such as explosions occurring from the amount of methane in the mine lit by the lamps of the miners, or cave-ins resulting to people being buried alive - could also cause hearing loss from the loud noises emitted by the machines used to drill through the rock, combined with the small enclosed spaces that the miners are in 4. Importance - mining is important because the minerals extracted from it are necessary in our daily lives such as coal, aluminum, oil, diamonds, and many more that we use in our daily lives.