Earth Materials

1. Earth Materials Rocks and Minerals

2. Minerals • inorganic solids • chemical composition • compounds • atoms joined together • individual elements • ex. gold (Au), sulphur (S) • two or more elements • ex. halite (NaCl)

3. Periodic Table of the Elements

4. Minerals, cont. • Most of the common minerals are made of crystals • What cause that crystalline characteristic? • regular arrangement of the compounds.

5. Mineral Properties • useful for identification • color • some mineral types occur in many colors • streak: color of mineral powder

6. Mineral Properties, cont. • luster • metallic vs. nonmetallic • hardness • ability or resistance to scratching • Moh scale (1 to 10) • 1 is softest; 10 is hardest • In 1822 a German scientist by the name of Frederick Mohs set up a scale to determine the approximate hardness of minerals.

7. Mineral Properties, cont. • cleavage • whether or not mineral split or crack along parallel or flat planes • These planes along which the mineral breaks are called cleavage planes. • If the mineral splits easily along these planes the mineral is then said to have perfect cleavage . • Mica is a good example of perfect cleavage. • Quartz shatters likes glass when struck with a hammer – No cleavage

8. Mineral Properties, cont. • density • weight per unit volume • crystalline patterns • miscellaneous properties • ex. talc has a distinctive feel

9. Mineral Types • Silicates • contains mainly compounds of silicon and oxygen • may also contain metallic elements such as iron or magnesium • 75% of Earth’s minerals quartz

10. Mineral Types, cont. • nonsilicates • remaining 25% • variety of types • native elements • ex. Copper: Cu • combination of elements • ex. Carbonates • Calcite: CaCO3 • Dolomite: CaMg(CO3)2

11. What eight elements make up over 98% of the Earth's crust? Note: They are, in decreasing quantity as you read downward

12. The Geologic Cycle Figure 11.5

13. Rocks • Mostly composed of a combination of minerals • ore deposit • large concentration of an individual mineral

14. Rocks Cycle • The rock cycle represents the alteration of rock-forming minerals above and below the Earth's surface. • three categories of rocks • igneous • sedimentary • Metamorphic • How they transform?

15. Igneous RocksFrom Latin word : “ignis” or fire • Forms from the cooling and crystallization of magma or lava • Two main classification schemes: a) texture b) chemistry • Classes by texture • Extrusive Igneous rock • Forms at the earth’s surface as lave cools • ex. Basalt (dark, fine grained) - Pumice (full of holes) , Obsidian (glassy)—pg 335 • Intrusive Igneous rock/Plutonic rocks • Forms deep underground where magma cools slowly. • have a coarse, crystalline texture • ex. granite

16. Classified by Chemical composition • Felsic • Word derived from Feldspar and Silica • High in silica (65% + • Usually light colored • Ex. Rhyolite (extrusive) Granite (intrusive) • Mafic • Word derived from Magnesium and Ferric (iron) • Low silica content (45-55% or so) • Usually dark-colored • Examples: Basalt (extrusive) and Gabbro (intrusive) • In some text : You may find more divisions based on chemical composition: • Intermediate , Ultramafic • Note: Silica is Silicon dioxide (SiO2)

17. Pluton • Any intrusive igneous rock can be further divided by size and orientation • Batholith • Laccolith • Dike • Sill Figure 11.7

18. Sedimentary Rocks • derived from preexisting rocks, or from organic materials • The exogenic processes of weathering and erosion generate the material sediments needed to form these rocks. • deposition, compaction, and cementation CATEGORIES: 3 categories • Detrital/ Clastic • ex. conglomerate, sandstone

19. Sedimentary Rocks, cont. • chemical types • precipitated from water • ex. Rock salt (halite) limestone (calcium carbonate) • biochemical (organic) types • ex. coal

20. Metamorphic Rocks Rocks altered in their physical and/or chemical composition by intense heat and/or pressure Metamorphism involves the transformation of a pre-existing rock to form new minerals and textures. Preexisting rock Metamorphic Rock plutonic rocks gneiss

22. Metamorphic Rocks, cont • Pre-existing rock Metamorphic Rock • shale slate

23. Metamorphic Rocks, cont • Pre-existing rock Metamorphic Rock • slate schist

25. Gneiss

26. Metamorphic Rocks, cont • Pre-existing rock Metamorphic Rock • limestone marble

27. Metamorphic environments & Processes • Metamorphism occur by two processes: • contact metamorphism • a magma intrusion bakes or recrystallizes rock in a localized area) • occurs under low to moderate pressure and low to high temperature conditions • Temperatures -- vary widely from 400-1000°C. Or… (2) regional metamorphism • where large scale deformation occurs from large scale compression or heating in areas.

28. METAMORPHIC ROCKS TYPES • Meta. rocks broken down into 2 groups: 1. Foliated metamorphic rocks • Usually associated with regional metamorphism Creates rocks with minerals in distinct bands • Most commonly occur at boundary of tectonic plates • directed pressure • flattens and lengthens the rock in the direction of greatest pressure • Examples of foliated meta. rocks = gneiss & slate. • Non-foliated metamorphic rocks • Usually associated with contact • Lack banding of minerals • Largely occurs formed by Burial metamorphism in deep basins • Examples of non-foliated metamorphic rocks are : • marble • quartzite. Quartzite