Classifying Rocks

Classifying Rocks

6.E.2.1 Summarize the structure of the Earth, including the layers, the mantle and core based on the relative position, composition and density.

6.E.2.1 Summarize the structure of the Earth, including the layers, the mantle and core based on the relative position, composition and density.

• Are made of mixtures of minerals and other materials, although some may contain only a single mineral.– Granite• Quartz• Feldspar,• Mica• Hornblend

Rocks

• When examining a rock, you must look at the inside of the rock because the effects of ice, liquid water, and weather can change the outer surface of the rock.

• When studying a rock sample, geologists observe the rock’s mineral composition, color, and texture.

Rocks

• About 20 minerals make up most rocks of Earth’s crust. The minerals are known as rock-forming minerals.

• A rock’s color provides clues to the rock’s mineral composition. For example, granite is generally a light-colored rock that has high silica content. Basalt is a dark-colored rock that is low in silica.

Mineral Composition

• Geologist observe the shape and color of crystals in a rock to identify the minerals that the rock contains.

• In identifying rocks, geologists also use some of the tests that are used to identify minerals.

• Acid tests are used to test for carbonates.• Magnetic tests are used to test for iron and

nickel.

Mineral Composition

Characteristics

Group D Group E Group F

Density Hardness Porous

Group A Group B Group C

Rock Color Texture Luster

• As with minerals, color alone does not provide enough information to identify a rock. But a rock’s texture is very useful in identifying a rock. Most rocks are made up of particles of minerals or other rocks, which geologists call grains. Grains give a rock its texture. To a geologist, a rock’s texture is the look and feel of the rock’s surface. Some rocks are smooth and glassy. Others are rough or chalky.

Texture

• Size, shape and pattern of rock grains.– Grains- particles of minerals or other rocks.

Texture

• Course Grained- Large and easy to see.

• Fine Grained- small.

Texture (Grain Size)

• Grains vary widely.– Tiny particles of sand.– Look like seeds– Crystals– Smooth / rounded– Jagged

Texture (Grain Shape)

• Grains often form patterns.

– Some lie in flat layers.

– Rows of grains.

– Random grains.

Texture (Grain Pattern)

• Have no grain.– They cool very quickly

when they form, gives the rock a smooth, shiny texture like thick glass. (obsidian)

– Or made out of extremely small particles of silica that settle out of water. (flint)

Texture (No Visible Grain)

• 3 Groups- refers to how the rocks formed.Igneous

• Forms from cooling molten rock.• Magma-

below the surface.

• Lava- above the surface.

Sedimentary

• Forms from particles of other rocks, remains of plants and animals that are pressed and cemented together.

Metamorphic

• Forms from pre-existing rock, deep underground.

• Changes rock with heat, pressure and chemical reactions.

Origin

Rock Cycle

Metamorphic

Igneous Sedimentary

MoltenMaterial

Pressure

A rock’s _________ provides clues to the rock’s mineral composition. A. shape B. size C. color D. diameter

Questions

What gives a rock its texture? A. Grains B. Color C. Size D. None of the above

What the three basic types of rocks? A. Microscopic, Normal, & Gigantic B. Igneous, Settlement, & Metamorphic C. Igneous, Sedimentary, & Metabolism D. Igneous, Sedimentary, & Metamorphic

The End