Minerals Rocks Earth Science Rocks and Minerals 20

Minerals & Rocks Earth Science: Rocks and Minerals (20: 00 min)

Minerals • Minerals are pure substances made up of only one type of matter through the process of crystallization. – Crystallization is the process by which atoms are arranged to form a material with a crystal structure. 1. melted materials (magma or lava) – Deep Magma = slow cooling & large crystals – Shallow Magma = faster cooling & small crystals – Lava = fastest cooling & no crystals 2. materials dissolved in water – Calcite – weathering from carbon dioxide.

Characteristics of Minerals • Characteristics: 1. Are naturally occurring • Cannot be man made 2. Inorganic • Cannot come from something once living 3. Definite chemical composition • Element = single atom. – • Gold (Au), Silver (Ag), Iron (Fe) Compound = two or more elements combined. – Calcite (Ca. CO 3), Talc (Mg 3 Si 4 O 10(OH)2)

Identifying Minerals • Each mineral has its own specific property used to identify it: 1. Hardness • The resistance of a mineral to being scratched. – Mohs Hardness Scale: » 1 = softest (Talc), 10 = hardest (Diamond)

selenite Fingernail (2 -3) Copper Strip (3) Glass Plate (5. 5 -6) microline Porcelain Streak Plate (6. 5 -7) 9

Identifying Minerals 2. Streak • The color of the powder left after being rubbed on a tile.

Identifying Minerals 3. Luster • The ability of a mineral to shine or reflect light. – Metallic – Dull – Pearly – Vitreous

Identifying Minerals 4. Cleavage • The tendency of a mineral to break along regular surfaces in one or more specific directions.

What is a Rock? • A mixture of minerals and other materials. – Granite = quartz, feldspar, mica and hornblende. • Geologists study and classify rocks based on: – Color – Texture – Mineral composition

Texture • Texture is look and feel of the rock’s surface. – Grains give a rock its texture. • Grain Size: coarse, fine or no visible grains • Grain Shape: Rounded, jagged • Grain Pattern: Banded or nonbanded.

Rock Types 3 Major groups of rocks: 1. Igneous Rock – Come from the cooling and crystallization of extremely hot liquid rock (lava or magma) • • • Slow cooling = large crystals Rapid cooling = small crystals Extra-fast cooling = no crystals – First rock type to have formed on Earth – “Igneous” = Greek for “fire”

Classifying Igneous Rocks • Origin Extrusive – lava cooling at Earth’s surface Intrusive – Magma cooling within Earth’s crust. – – • Texture Fine grained – rapid cooling coarse grained – slow cooling – – • Mineral Composition – • – • Mafic (Iron & Magnesium) dark colored Felsic (Aluminum) light colored

Rock Types 2. Sedimentary Rock – Particles of rocks or remains of plants and animals that are compacted and cemented together. • Deposited in layers by water, wind and ice. • Classified into 3 groups based on how they were made: – Organic – formed from remains of living things; plants and animals – Chemical – formed when elements dissolved in water came out of solution. – Clastic – formed when particles that were weathered from other rocks were cemented together.

Shell Limestone

Rock Types 3. Metamorphic Rocks – “Changed Rock” – When existing rock; sedimentary, igneous or metamorphic, has its texture, structure and composition changed by heat, pressure or chemical reactions. • Two texture groups: – Foliated – platy or leaf-like minerals (mica or chlorite) are nearly aligned parallel to one another. • Splits along well-oriented, parallel lines – Non-foliated – randomly oriented platy minerals, massive. • Break into angular pieces

The Rock Cycle • A series of processes on Earth’s surface and inside the planet that slowly change rocks from one kind to another = rock cycle. – Builds, destroys and changes the rocks in the crust. • What process drives the rock cycle? Plate Tectonics

The Rock Cycle

The Rock Cycle • Rock formed from the cooling of melted rock is called: Igneous Rock • Rock formed by weathering and erosion is called: Sedimentary Rock • Rock formed by heat and pressure is called: Metamorphic Rock