2 Minerals the building blocks of rocks Mineral Characteristicsnaturalinorganicsoliddefinite compositioncrystal structure
3 Mineral Formation 4 major processes by which minerals form: 1. Crystallization from magma- cooling magma causes minerals to crystallize
4 2. PrecipitationMinerals dissolve out of evaporated water; precipitated
5 3. Pressure and Temperature Change in pressure and temperature cause an existing mineral to recrystallize while still solidMuscoviteTalc
6 4. Hydrothermal Solutions A hot mixtures of water with substances dissolved in them. When they come in contact with existing minerals- a chemical reaction occurs forming a new mineralBornite
7 Mineral CompositionMinerals are grouped or classified based on their composition. There are 6 groups1. Carbonates - contain carbon, oxygen, and one ore more metallic element
8 2. Silicates formed from silicon and oxygen elements combined to form a silicon tetrahedron, 1 silicon atom and 4 oxygen atomsformed from cooling magmaeither near the surface (few crystals) or deep below surface (larger crystals)
9 3. Oxides- Minerals that contain oxygen and one or more other element(s)
10 Gypsum4. Sulfates and Sulfides- Minerals containing sulfurPyrite
11 5. HalidesHalite-minerals containing halogen ions plus one or more other elements
12 6. Native ElementsMinerals that exist in a relatively pure form gold, silver, copperGold crystal structure
13 Mineral PropertiesMineral PROPERTIES are used to identify minerals based on specific characteristicsLuster Streak Color Specific Gravity Cleavage & Fracture Hardness Magnetism Fluoresence
14 Streak color of a mineral in its powder form Color often not a good property for Iding
15 Luster how light is reflected from the surface of a mineral
16 Cleavage- tendency to break along flat, even surfaces (mica) Fracture- uneven breakage (quartz)
17 Specific Gravity- ratio of a mineral’s density to the density of water mass (g) of dry samplemass lost in waterSpecific Gravity is a ratio…soSpecific Gravity has no units
18 Hardness- measure of resistance of a mineral being scratched
21 Rocks- any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet There are 3 major type or families or rock:Igneous rocksSedimentary rocksMetamorphic rocks
22 Igneous Rocks Magma- molten material underground Lava- magma that reaches the surfaceIgneous rocks are formed from magma that has cooled and hardened either beneath the surface or from a volcanic eruption
23 2 Ways to Form Igneous Rock Intrusive Igneous Rocks- form when magma hardens beneath Earth’s surfaceMagma intrudes into existing rocksExtrusive Igneous Rocks- form when lava hardens on the surface of the EarthExtruded onto the surfacerhyolitegranite
24 Magma contains some gases, including water vapor- this make it less dense, so it rises As magma rises, it cools and forms crystalsThe longer the cooling time the larger the crystals
25 Classification of Igneous Rocks Igneous rocks are classified by texture and composition Texture refers to the appearance of an igneous rock (size, shape, arrangement of crystals)Composition refers to the proportions of light and dark minerals in the rock
26 Coarse- grained Texture- form as a result of slow cooling, ions can move = large crystal size Fine-grained Texture- form as a result of quick cooling time, ions lose motion= small crystal sizeGlassy Texture- form from lava that cools rapidly, ions don’t have time to arrange = glassy texturePorphyritic Texture- rocks with different size minerals that form from varying cooling rates
27 Felsic Composition- contain mainly quartz and feldspar, some with biotite mica and amphibole. Make up major rocks of continental crustMafic Composition- contain mainly dark colored minerals and feldspar, along with Mg and Fe. Darker and denser than granitic composition
28 Classification of Major Igneous Rocks Texture is crossed with composition to classify igneous rocks. For example, granite has a coarse texture due to slow cooling and larger crystals, and a light color from the light colored quartz and feldspar minerals used to form it.
29 Sedimentary Rocks- formed from compacted and cemented sediments Weathering physically and chemically breaks rocks into small pieces called sedimentsSediments are movedby wind, water, ice,and gravityEventually, they are dropped and form layers that are cemented together
30 Weathering, Erosion, and Deposition Weathering breaks rocks downErosion involves weather and the removal of rockDeposition is the dropping of sedimentsSediments are deposited according to size
31 Compaction and Cementation Compaction is the process that squeezes the water out of the sediments. It is caused by the weight of the sediments.Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.Cementing holds the sediments together.
32 Classification of Sedimentary Rocks Clastic Sedimentary Rocks are formed from weathered bits of rocks and mineralsOrganic Sedimentary Rocks are formed from living materialsChemical Sedimentary Rocks are formed when dissolved minerals precipitate from water solutionrock saltlimestone
33 Sedimentary rocks hold many clues to the Earth’s history Layers of sediments are records of geologic events on EarthFossils are unique to sedimentary rocks
34 Sedimentary rocks drop according to size; larger particles fall first followed by smaller particles
35 Metamorphic Rocks- form when existing rocks undergo change through heat and pressure Metamorphism means to changeMost metamorphic changes occur at high temperatures and pressureThese occur deep below the Earth’s surface and extend into the mantle
36 Forms of MetamorphismContact Metamorphism- forms when magma intrudes into existing rockChanges in rocks are minorRegional Metamorphism- formed during mountain building process that occur over a large areaMajor changes to rocks
38 Agents of Metamorphism Heat- causes existing minerals to recrystallize or new minerals to formPressure- causes the spaces between mineral grains to close= more compact rock= greater density
39 Classification of Metamorphic Rocks- based on texture and composition Foliated Metamorphic Rocks- form when minerals recrystallize at right angles to the direction of forceCauses a layered or banded appearanceNonfoliated Metamorphic Rocks- no banded textureMost contain only one mineral
43 Thinking about relationships among the major rock groups The Rock CycleThinking about relationships among the major rock groups
44 Major Rock Groups Igneous Sedimentary Metamorphic Formed from a melt (molten rock)Plutonic (intrusive):slow cooling and crystallizationVolcanic (extrusion): quick cooling at the surfaceSedimentaryFormed at the Earth’s surfaceClastic (Mineral Fragments or grains, clays)Chemical (crystalline chemical/biochemical precipitates)Organic (made from living material: shells, plants)MetamorphicChanged by pressure, heat and fluids.
57 In Conclusion…The rock cycle demonstrates the relationships among the three major rock groupsIt is powered by the interior heat of the EarthAs well as earth’s momentum and…The energy from the sunIt involves processes on the Earth’s surface as well as the Earth’s interiorIt connects the “hydrologic cycle” with the “tectonic cycle”.
Your consent to our cookies if you continue to use this website.