1. Minerals and Rocks Ch 6 8 th grade

2. 6.1 Vocabulary Inorganic Crystal Streak Luster Cleavage Fracture Geode Crystallization Solution Vein

3. What is a Mineral? A mineral is a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. A substance must have all 5 to be a mineral.

4. Naturally occurring: formed by nature Solid: definite volume and shape Inorganic processes: not formed from organisms Crystal structure: particles line up in a repeating pattern Definite chemical composition: always contains certain elements in specific ratio

5. How are Minerals Identified? Color: only a few minerals have their own characteristic color. Streak: does not vary, and often is not the same as the color Luster Hardness: most useful characteristic, Mohs hardness scale assigns a ranking 1 (talc) to 10 (diamond); determined by a scratch test: mineral scratches a softer mineral and will be scratched by a harder mineral

6. Density: no matter the size of a sample, the density remains the same; a balance determines the mass and water displacements determines the volume: Density= mass/volume Crystal structure: all crystals of a mineral have same structure; light bounced off a small crystal will produce distinct patterns; crystals are classified by number of faces (sides) and the measure of the angles at which the faces meet.

7. Cleavage and Fracture: cleavage is determined by the arrangement of atoms; otherwise, the characteristic type of fracture is seen Special Properties: some minerals may bend light; conduct electricity, glow under UV light; or are magnetic

8. How do Minerals Form? 1.Some minerals form from organic processes. 2.When elements and compounds that are dissolved in water leave a solution, crystallization occurs. –Some minerals form when solutions evaporate. –When hot water dissolves elements and then begins to cool, the elements crystallize as minerals. Pure metals that crystallize from hot water solutions often form veins.

9. 3.Some minerals form when magma and lava cools. Size of crystals depends upon: -- amount of gas the magma contains, -- chemical composition -- rate at which it cools:  magma cools slowly so large crystals form  lava cools quickly creating small crystals. Magma and lava contains oxygen and silicon that create silicates that make up a majority of Earth’s crust

10. Earth’s crust is made of common minerals. Less common minerals are not found evenly throughout the crust. These minerals are deposited in concentrated areas called ores. Forming crystals

11. 6.2 Vocabulary Rock-forming mineral Granite Basalt Grain Texture Three Main Rock Types

12. How Do Geologist Classify Rocks? Mineral composition and color: –Rocks are made of mixtures of minerals and other materials and some contain only a single mineral. –About 20 minerals make up most of the Earth’s crust. –A rock’s color provides clues to its mineral composition, but does not provide enough information to identify it.

13. Texture: –Most rocks are made up of grains that give the rock its texture. –To describe texture, terms are used based on size, shape, and grain pattern. Size: large grains are easy to see and called coarse grained while fine-grained rocks have small grains Shape: results from the shape of the mineral crystals or the jagged bits of several rocks Pattern: banded rocks with grains that form layers of colored swirls or nonbanded rocks with no visible pattern.

14. Origin (how the rock forms): –Igneous: formed from cooling of magma or lava –Sedimentary: forms layers of small particles of rock or remains of organisms that are pressed and cemented together –Metamorphic: forms when a rock is changed from heat, pressure, or by chemical reactions.

15. Geology Kitchen: The 3 Types of Rocks

16. 6.3 Vocabulary Rock cycle

17. What is the Rock Cycle? Forces deep inside Earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust.

18. While there are many pathways through the rock cycle, a common one is: –Granite forms below Earth’s surface as magma cools (so it’s igneous rock). –Earth’s forces push the granite upward and weathering and erosion wear it away into sand carried to the oceans –Layers of sand pile up. Either it gets compacted or cemented by calcite to become sandstone (now sedimentary rock). –Pressure builds and silica (from the quartz in the granite) replaces the calcite. The rock changes from gritty to smooth: from sandstone to quartzite (a metamorphic rock).

19. The changes of the rock cycle are closely related to plate tectonics. Plate movements help drive the rock cycle by helping to form magma, the source of igneous rock. Where oceanic plates move apart, magma moves upward and fills the gap with new igneous rock. Where an oceanic plate is subducted, magma forms and rises. A collision of plates may push rocks so deep that they melt to form magma

20. The collision of plates can be strong enough to push up a mountain range. Then destructive forces begin which leads to the formation of sedimentary rock. A collision of plates can also push rocks deep down beneath the surface. Heat and pressure could change the rock into metamorphic rock. As the rock on the Earth moves through the rock cycle, material is not lost or gained, simply changed forms.

22. Rock Cycle Rock Cycle Foldable Rock Cycle Modeled Out of Crayons