Chapter 9 : Rocks and Minerals

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Table of Contents

Chapter 9 : Rocks and Minerals Section 1: Minerals—Earth’s Jewels Section 2: Igneous and Sedimentary Rocks Section 3: Metamorphic Rocks and the Rock Cycle

Section 1 – Minerals • You will: • Identify the difference between a mineral and a rock. • Describe the properties used to identify minerals • Examples of minerals around us and its uses:

Ex of Minerals • Muscovite – used in insulators

Sulfur – used for matches, explosives, tires, fertilizers

Pyrite or Fool’s Gold Looks like gold but it is not. Used in jewelry

Magnetite – used to make magnets

Calcite - Used in medicines, soil conditioner, roadbed material, and building stone.

Feldspar – ceramics, glass, enamel, soap, false teeth and silverware.

optical instruments, and electrical devices. Used in making sand paper and grinding tools.

Pink Quartz – jewelry and ornamental objects

Amethyst – jewelry and medicines

A mineral is always- 4 important characteristics : 1)formed by natural processes – not man made 2)Minerals are inorganic – can’t come from plants or animals 3)Minerals have a definite chemical composition – formed always by the same types of chemical elements

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Composition: Most of the rock-forming minerals are:

1) silicates which contain the elements silicon and oxygen 2) carbonates which contain carbon and oxygen

1 LAST IMPORTANT CHARACTERISTIC

4) Minerals are crystalline solids Crystalline means that the atoms in these solids are arranged in repeating patterns Ex: next slide

The surfaces show crystalline pattern

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What are Crystals ? • Solid materials that have a structure with a repeating pattern of atoms • Minerals are also called crystals

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Rocks x Minerals

Minerals: naturally occurring, inorganic, solid materials, with a definite chemical composition and a crystalline internal arrangement Rocks: usually are made of two or more minerals.

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Rocks x Minerals

**MINERALS are considered the building blocks of rocks!

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How do minerals form? 4 different processes: 1) From magma (melted rock that is inside the Earth) – minerals form inside the Earth

2) From lava (magma that reaches the Earth’s surface after volcanic eruptions) – minerals form on the Earth’s surface

1 How do minerals form? 3) Evaporation - salt and other minerals can crystallize when sea water evaporates 4) Precipitation – when there is too much dissolved materials in water, the excess can crystallize.

• The size of the crystals depend partially on how rapid the magma cools • Cools fast - crystals are small • Cools slow – crystals are bigger . Will have more time to form.

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Gems:

• are minerals that are rare and can be cut and polished, giving them a beautiful appearance. • Very expensive because they are rare • Ideal for jewelry

Geodes are holes in rocks that have crystals around the inside

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Ores – are combinations of rocks and minerals

• This combination of rocks and minerals is an ore only if:

• contains enough of a useful substance that it can be sold for a profit. • the ore must be extracted from Earth in a process called mining.

Minerals—Earth’s Jewels

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Ore Processing

• After an ore has been mined, it must be processed to extract the desired mineral or element. • Smelting melts the ore and then separates and removes most of the unwanted materials.

Minerals—Earth’s Jewels

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Ore Processing

• After this smelting process, it can be refined, which means that it is purified.

Minerals—Earth’s Jewels

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Examples of Ores:

• Steel comes from iron that is extracted from hematite • lead for batteries is produced from the mineral galena

• magnesium used in vitamins comes from the mineral dolomite.

Gold Ores

Minerals are considered a nonrenewable resource • It takes millions of years to form minerals • It is important to recycle all materials obtained from minerals • To recycle iron and steel could reduce the extraction of the mineral hematite, protecting this natural resource

Section 2 and 3: Rocks and the Rock Cycle • • • •

There are 3 different types of rocks: Sedimentary Igneous Metamorphic Each type go through different natural process that will form them.

Igneous and Sedimentary Rocks

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Igneous Rock

• Igneous rocks form when melted rock material ( magma) from inside Earth cools. 2 types:

• Extrusive • Intrusive

Igneous and Sedimentary Rocks

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• Extrusive igneous rocks form when melted rock material cools on Earth’s surface. When the melted rock reaches Earth’s surface, it is called lava. Extrusive Rocks form from lava

Rocks from Lava 2

• Magma can reach the Earth’s surface due to volcanic eruptions or fissures (openings) on the Earth’s surface.

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Rocks from Lava • Lava cools quickly before large mineral crystals have time to form, so these rocks are composed of small minerals

Igneous and Sedimentary Rocks

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• Intrusive igneous rocks are produced when magma cools below the surface of Earth. ( it is not lava)

Igneous and Sedimentary Rocks

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Rocks from Magma • Intrusive igneous rocks generally have large mineral crystals that are easy to see – they have time to cool and form the big minerals

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Chemical Composition and color • The chemicals in the melted rock material determine the color of the rock.

Granitic Igneous Rocks - High percentage of silica – rocks are light in color – usually intrusive – coarse grained

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Chemical Composition and color

Basaltic Igneous Rocks – high percentage of iron, magnesium or calcium – darker – usually extrusive – Fine grained

Andesitic Igneous Rocks • Andesitic igneous rocks have mineral compositions between those of basaltic and granitic rocks. • Igneous rocks can be: • basaltic, granitic and andesitic intrusive • basaltic, granitic and andesitic extrusive

Igneous and Sedimentary Rocks

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Sedimentary Rocks • Made of compacted sediments. • Sediments - Pieces of broken rock, shells, mineral grains, and other materials • Sediments are dropped by wind, water, gravity and can be compacted in layers forming Sedimentary Rocks

• *Sedimentary rock forms when layers of sediments accumulate (1). • As the sediment accumulates, the weight of the layers of sediment presses down and compacts (2) the layers underneath. • The sediments become cemented (3)together, as layers, into a hard rock

Igneous and Sedimentary Rocks

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Sedimentary Rocks • Most sedimentary rocks take thousands to millions of years to form.

• There are 3 types: • Detrital • Chemical • Organic

Igneous and Sedimentary Rocks

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Detrital Rocks

• Detrital rocks are made of grains of minerals or other rocks that have been compressed • Ex: Book page 269, Figure 17 for examples

Igneous and Sedimentary Rocks

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Chemical Rocks

• Chemical sedimentary rock forms when mineral-rich water from geysers, hot springs, or salty lakes evaporates. • As the water evaporates, layers of the minerals are left behind, forming a rock

Limestone – chemical sedimentary rock

Igneous and Sedimentary Rocks

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Organic Rocks

• Form by: Living matter that dies, piles up, and then is compressed

into rock. EX: • Chalk and coal

Igneous and Sedimentary Rocks

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Organic Rocks

• Coal is produced from layers of plants • Chalk is formed from calcium carbonate that form the skeleton of small marine animals that will deposit on the bottom of the sea

Limestone – organic or chemical sedimentary rock Limestone is organic when has fossils in it. - It is also formed from the mineral calcite when the ocean water evaporates, such as the chemical sedimentary rock limestone - But contains also remains of once living organisms

**Fossils and Sedimentary Rocks Sedimentary rocks can contain fossils because unlike other rocks, they will form at temperatures and pressure that do not destroy the rests of the organisms Dead organisms can, under the right conditions, become sediments and form Sedimentary rocks

Metamorphic Rocks and the Rock Cycle

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Metamorphic Rocks • Metamorphic means “change of form”

• Metamorphic rocks form when existing rocks are heated or squeezed. • It is a process that takes millions of years

Metamorphic Rocks and the Rock Cycle

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Examples:

• limestone can change to marble.

Metamorphic Rocks and the Rock Cycle

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Types of Metamorphic Rocks

• It depends on the TEXTURE: • foliated and nonfoliated.

Metamorphic Rocks and the Rock Cycle

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• Foliated rocks have visible layers • These minerals have been heated and squeezed into parallel layers, or • Many foliated rocks leaves. have bands of differentcolored minerals. • Gneiss pg 273

Metamorphic Rocks and the Rock Cycle

3 • Nonfoliated rocks do not have distinct layers or bands.

• Ex: quartzite, marble, often are more even in color than foliated rocks. • Page 273

Metamorphic Rocks and the Rock Cycle

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Read “The Rock Cycle” page 275 • rock cycle is a model to describe how different kinds of rock are related to one another and how rocks change from one type to another.

• There are several processes involved

Weathering – rocks are broken down into sediments Erosion - sediments are transported to other places by wind, water, ice, gravity Melting – liquefy Heat and pressure Cooling

Compaction – sediments are pressed Cementation – minerals dissolve in the presence of water creating a “cement” that will glue the sediments together Diagram page 275 – the different colors on the arrows represent the different processes that will transform one type rock into another.