Rocks &

Minerals

Lesson 1Properties of Minerals

What is a mineral?

● A mineral must have 5 specific characteristics to be considered a mineral

a. Naturally occurring - formed by natural processes. b. Solid - must have a definite shape and volume. c. Crystal structure - the repeating pattern of a mineral’s particles form a solid called a

crystal.d. Inorganic processes - formed from materials that are not part of living things. e. Chemical composition - minerals always contain specific elements in specific

amounts.

What is a mineral?

● Almost all minerals are compounds○ In a compound, two or more elements are combined and end

up with the same properties ○ Cinnabar is made of sulfur (a yellow solid) and mercury (a

silver liquid) and looks like shiny red crystals!

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What is a mineral?

● Different minerals are made of different elements○ A crystal of quartz is made up of one atom of silicon and two

atoms of oxygen○ Garnet minerals are made up of three atoms of silicon for

every twelve atoms of oxygen

How are minerals identified? ● Geologists have identified more than 4,000 minerals● Each mineral has characteristic properties that are used to

identify it:○ Color - only a few minerals have their own unique color.○ Streak - the streak of a mineral is the color of its powder. The streak color and color

of the actual mineral are usually very different! ○ Luster - luster is how the mineral looks, either metallic or silky or waxy or glassy! ○ Hardness - the Mohs Hardness Scale is used to rank the hardness of minerals from

1-10 by using a scratch test.

How are minerals identified? ● Each mineral has characteristic properties that are used to

identify it:○ Density - the mass of the sample is divided by the volume. ○ Crystal structure - minerals have crystals that are shaped differently that are

classified by the number of faces or sides on the crystal.○ Cleavage & fracture - a mineral that splits easily along flat surfaces has a property

called cleavage. Minerals that split in very irregular patterns have a property called fracture.

○ Special properties - conducting electricity, glowing under UV light, or magnetism.

How do minerals form?

● A geode is a rounded, hollow rock that is lined with mineral crystals ○ Crystals form inside a geode when water seeps into a crack of the rock ○ Over time, crystallization occurs - the process where atoms are arranged to form a

substance that has a crystal structure

● Generally, minerals form in 3 ways:○ By organic processes○ From solutions○ As magma and lava cool

How do minerals form?

● Minerals form from organic processes○ Clams and corals produce shells made out of the mineral calcite

● Minerals form from solutions○ A solution is a mixture where one substance is dissolved in another○ When an element or compound is left in water, crystallization occurs○ When a solution evaporates, the water leaves behind crystals

● Minerals form from magma and lava○ As hot magma or lava cools to a solid state, they form crystals○ Size of crystals depends on how fast the magma cools, the amount of gas in the

magma, and the chemical composition of the magma

How do minerals form? Examples of minerals formed from each process

By evaporation By lava cooling By magma cooling By how water solutions

Halite, gypsum, calcite Leucite, olivine Quartz, feldspar, tourmaline, mica

Selenite, silver, gold, quartz

Where are mineral resources found? ● Earth’s crust is made of the rock-forming minerals

○ Less common minerals are not found in Earth’s crust, they are brought together in deposits■ An ore is a deposit of valuable minerals contained in rocks■ Ores are mined and the mineral is separated from the rock, like iron, lead, graphite, sulfur Lesson 2

Classifying Rocks

How do geologists classify rocks? ● To study a rock sample, geologists observe

the rock’s mineral composition, color, and texture ○ Mineral composition

■ Rocks are made of minerals and other materials ■ Some rocks only contain one mineral, while

others have several minerals ● Granite is made of quartz, feldspar, mica,

and hornblende■ About 20 minerals make up the rocks of Earth’s

crust, which are all called rock-forming minerals

How do geologists classify rocks? ● To study a rock sample, geologists

observe the rock’s mineral composition, color, and texture○ Color

■ A rock’s color provides clues to the mineral composition

■ Granite is a light colored rock with a lot of silicon and oxygen

■ Basalt is a dark colored rock with less silicon and oxygen, but has tiny mineral crystals

How do geologists classify rocks? ● To study a rock sample, geologists observe the rock’s mineral

composition, color, and texture○ Texture

■ Most rocks are made of minerals, or other rocks, which geologists call grains

■ Grains give the rock its texture, the look and feel of a rock’s surface

■ To describe the texture of a rock, geologists use terms related to the size, shape, and pattern of the rock

How do geologists classify rocks? ● To study a rock sample, geologists observe the rock’s mineral

composition, color, and texture○ Texture

■ Grain size ● Rocks with large grains are coarse grained● Rocks with small grains are fine grained

■ Grain shape● Round grain rocks have mineral crystals that form the rock● Jagged grain rocks are made of jagged bits of several rocks

■ Grain pattern● In banded rocks grains lie in a pattern of flat layers or form swirls or

colored lines ● In non-banded rocks there is no visible pattern to the grains

How do geologists classify rocks? ● Geologists use the color, texture, and mineral composition of a

rock to determine its origin, or the way the rock was formed ● Geologists have classified rocks into three major groups:

○ Igneous rock○ Sedimentary rock○ Metamorphic rock

How do geologists classify rocks? ● Igneous rock

○ Forms from the cooling of magma or lava ■ Magma hardens underground to form rock = intrusive rock■ Lava hardens to form rock on Earth’s surface = extrusive rock

● Sedimentary rock○ Forms when small particles of rocks or remains of plants and

animals are pressed together ■ Forms in layers below the surface of the rock

● Metamorphic rock○ Forms when a rock is changed by heat or pressure, or by chemical

reactions ■ Most metamorphic rock forms deep underground

Lesson 3 Igneous Rocks

How do geologists classify igneous rocks?

● Igneous rocks are classified by their origin, texture, and mineral composition○ Origin

■ Igneous rocks may form on or beneath Earth’s surface ■ Extrusive rock is igneous rock formed from lava on Earth’s surface

● Basalt is the most common extrusive rock■ Intrusive rock is igneous rock formed from magma underground

● Granite is the most common intrusive rock

How do geologists classify igneous rocks?

● Igneous rocks are classified by their origin, texture, and mineral composition○ Texture

■ Depends on the size and shape of its mineral crystals ■ Rapidly cooling lava forms fine-grained igneous rocks with little to no

crystals ■ Slow cooling magma forms coarse-grained igneous rocks with large crystals

How do geologists classify igneous rocks?

● Igneous rocks are classified by their origin, texture, and mineral composition○ Mineral composition

■ Lava that has little silicon and oxygen form dark colored rocks like basalt● Basalt contains the minerals feldspar and other dark colored minerals

■ Magma that has a lot of silicon and oxygen form light colored rocks like granite

● Granite contains the minerals quartz, feldspar, hornblende, and mica

How are igneous rocks used?

● Igneous rocks are hard, dense, and durable● Many people use them for tools and building materials

○ Granite has been used for more than 3,500 years ■ It was first used to build statues and fortresses ■ Nowadays, it is used for bridges, buildings, flooring, cobblestones, and much

more!

○ Pumice and obsidian are other igneous rocks with building uses■ Pumice is used as an abrasive for cleaning and polishing ■ Obsidian has been used for sharp tools for cutting or scraping

Lesson 4 Sedimentary Rocks

How do sedimentary rocks form? ● Sediment is small, solid pieces of material that come from rocks or

living things ● Sedimentary rocks form when sediment is deposited by water and

wind○ Most sedimentary rocks are formed through a sequence of processes

i. Weathering & erosionii. Deposition

iii. Compactioniv. Cementation

How do sedimentary rocks form? ● Most sedimentary rocks are formed through a sequence of

processes○ Weathering & Erosion

■ Weathering is the effect of freezing and thawing, acid, plant roots, and other forces on rocks

■ After the rocks are broken up, the fragments are carried away by erosion, the process where running water, wind, or ice carry away broken-up rock

How do sedimentary rocks form? ● Most sedimentary rocks are formed through a sequence of

processes○ Deposition

■ Deposition is the process where sediment settles out of the water or wind carrying it and is deposited in layers on the ground of a lake or ocean

How do sedimentary rocks form? ● Most sedimentary rocks are formed through a sequence of

processes○ Compaction

■ Compaction is the process that presses sediment together ■ When new layers of sediment begin to build up, the older layers

beneath them are pressed together from the weight

How do sedimentary rocks form? ● Most sedimentary rocks are formed through a sequence of

processes○ Cementation

■ Cementation is the process where dissolved minerals crystallize and glue particles of sediment together

What are the 3 major types of sedimentary rock? ● Geologists classify sedimentary rocks according to the type of

sediments that make up the rock○ There are three major groups of sedimentary rocks:

■ Clastic ■ Organic ■ Chemical

What are the 3 major types of sedimentary rock? ● There are three major groups of sedimentary rocks

○ Clastic ■ Clastic rocks are formed when rock fragments are squeezed

together ● Fragments range in size from microscopic particles to large

boulders ■ Clastic rocks are grouped by the size of the fragments ■ Common clastic rocks are sandstone (made from sand on

beaches, ocean floors, riverbeds, etc.) and shale (made from clay particles)

What are the 3 major types of sedimentary rock? ● There are three major groups of sedimentary rocks

○ Organic ■ Organic rocks form where the remains of plants and animals

are deposited in layers ● Coal forms from the remains of swamp plants buried in

water ● Limestone forms in the ocean - when ocean animals die,

their shells pile up on the ocean floor and change into limestone over millions of years

What are the 3 major types of sedimentary rock? ● There are three major groups of sedimentary rocks

○ Chemical■ Chemical rocks form when minerals dissolved in a water

solution crystallize ■ Limestone can also be created this way! When calcite is

dissolved from the ocean animal shells in the sea water, it can form crystal limestone

■ Chemical rocks can also be formed when seas or lake evaporate and leave behind mineral deposits

How are sedimentary rocks used? ● People have used sedimentary rocks throughout history for

building materials and tools ○ Chert was used to make spearheads over 10,000 years ago○ Flint was used to make arrowheads ○ Sandstone and limestone are used as building materials (the White

House is made of sandstone!)

Lesson 5Metamorphic Rocks

What are metamorphic rocks? ● Any rock that forms from another rock as a result of changes in

heat or pressure (or both!) is a metamorphic rock○ Metamorphic rock can form from igneous, sedimentary, or other

metamorphic rock○ Many metamorphic rocks are found in mountains or near large

areas of igneous rock

How are metamorphic rocks formed? ● The heat that changes a rock into metamorphic rock can come

from pockets of magma inside Earth’s crust ○ These pockets of magma can rise up through the crust. Their high

temperatures change the rock into metamorphic rock! ○ Collisions between Earth’s plates also push down rock toward the

heat

How are metamorphic rocks formed? ● Very high pressure can also change rock into metamorphic rock

○ Plate collisions cause high pressure on rocks while mountains are being formed

○ This pressure can deform or change the shape of the rock ○ The deeper that a rock is buried in Earth’s crust, the greater

the pressure on it

How are metamorphic rocks classified?● Geologists classify metamorphic rocks according to the

arrangement of the grains making up the rocks ○ Foliated rocks

■ Foliated rocks have their grains arranged in parallel layers■ Slate is a common foliated rock that is formed when shale is under high heat

and pressure.

○ Nonfoliated rocks■ Nonfoliated rocks have randomly arranged grains■ Marble is a common nonfoliated rock that is formed when

limestone is under high heat and pressure.

How are metamorphic rocks used?

● Metamorphic rocks are important for building materials and sculptures○ Marble has an even grain, so it can be cut into thin slabs or carved

into many shapes, so it used for many statues and buildings (like the Tower of Pisa!)

○ Slate comes in many colors and splits evenly into flat pieces, so it is used for roofing, walkways, and for stone buildings

Lesson 6The Rock Cycle

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 Earth’s crust.

○ The rock cycle is a series of processes that occur on Earth’s surface and in the crust that slowly change rocks from one kind to another

The rock cycle and plate tectonics.

● The changes in the rock cycle are closely related to plate tectonics○ Plate movements help drive the rock cycle by helping to form each of

the 3 types of rock:■ When ocean plates move apart, magma moves up and fills in the gap with new

igneous rock■ The collision of continental plates can be strong enough to push up and create a

mountain range, then weathering and erosion begin to wear away the mountains and creates sedimentary rock

■ A collision of continental plates can also push rocks down deep beneath Earth’s surface, where heat and pressure change the rocks to metamorphic rocks

Conservation of material in the rock cycle.

● None of the rock that is destroyed during the rock cycle is lost○ For example, when a mountain erodes, the sediment will eventually

turn into new rock somewhere