EARTH’S STRUCTURE Chapter 2: Minerals and Rocks 2.1 Properties of Minerals

What is a Mineral? Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. Let’s break this down ---

What is a Mineral? Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. This means that minerals are formed by natural processes in and on Earth.

What is a Mineral? Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. This means that minerals are all solid, with a definite volume and shape. The particles are packed together tightly.

What is a Mineral?

Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. This means that minerals are formed from items that were not a part of a living organism.

What is a Mineral? Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. A crystal is a repeating pattern of flat sides (faces) that meet at sharp edges and corners.

What is a Mineral?

Mineral: a naturally occurring solid that can form by inorganic processes and that has a crystal structure and a definite chemical composition. A mineral always contains the exact chemical structure – the same elements are present in the same proportions.

What is a Mineral?

Minerals, Compounds, & Elements Almost all minerals are compounds. Compound: two or more elements that are combined so that the elements no longer have their own properties. Each mineral has a unique combination of elements. Some elements, like copper, silver, and gold, are also minerals.

Identifying Minerals Color: Many minerals share the same color Not a great way to identify the minerals

Identifying Minerals Streak: Color of the powder left behind from the mineral The streak is not always the same color as the mineral

Identifying Minerals Luster: How light is reflected from a mineral’s surface Metallic, glassy, earthy, silky, waxy, and pearly

Identifying Minerals Hardness: One of the most useful ways to identify minerals Mohs Hardness Scale ranks minerals from 1-10, with 10 being the hardest (Diamond) and 1 being the softest (Talc). Determined by a scratch test – scratch unknown mineral by known minerals to see if a scratch appears or not.

Identifying Minerals Density: Unique to each mineral Mass divided by volume Depends on how the atoms are arranged in the mineral

Identifying Minerals Crystal Structure: All crystals in a mineral have identical patterns Good to identify small samples Beams reflect light in specific patterns

Identifying Minerals Cleavage and Fracture: Cleavage: a mineral that splits easily along flat surfaces; depends on how the crystals are arranged. Fracture: a mineral breaks apart in an irregular way

Identifying Minerals Special Properties: Magnetism Glow in UV light Bends light Conducts electricity

CHAPTER 2: MINERALS AND ROCKS 2.2 Classifying Rocks

Classifying Rocks About 20 minerals make up most of the rocks on Earth’s crust. These are called rock-forming minerals. A rock’s color gives clues to the minerals that make it up. Granite is usually light colored and rich in oxygen and silica, while basalt is generally dark colored with a low silica content.

Classifying Rocks

Texture Grains give the rock its texture, the look or feel of a rock’s surface. Grain size: rocks with large grains are coarse grained, rocks with small grains are fine-grained rocks.

Texture Grains give the rock its texture, the look or feel of a rock’s surface. Grain shape: rounded grains form a conglomerate rock, jagged grains form breccia.

Texture Grains give the rock its texture, the look or feel of a rock’s surface. Grain pattern: patterned layers of grains form a banded rock, while rocks with no patterns are non-banded.

Rocks There are three main types of rocks: Igneous: forms from the cooling of magma/lava. Sedimentary: forms when small particles are pressed and cemented together. Metamorphic: forms when an already existing rock is changed by heat, pressure, or chemical reactions.

CHAPTER 2: MINERALS AND ROCKS 2.3 Igneous Rocks

Igneous Rocks These rocks are classified by their: Origin Texture Mineral composition

Origin Igneous rocks can form below or above ground. If they are formed below ground, they are made of magma and are said to be intrusive. Granite is the most abundant intrusive rock. If they are formed above ground, they are made of lava and are said to be extrusive. Basalt is the most common extrusive rock.

Origin

Texture Texture depends on the size and shape of its mineral crystals. Rapidly cooling lava forms fine-grained igneous rocks with small crystals or no crystals. (extrusive) Slow cooling magma forms coarse-grained rocks with large crystals. (intrusive)

Mineral Composition Lava low in silica usually forms dark rocks. Magma high in silica usually forms light rocks.

Uses for Igneous Rocks Because they are hard, dense, and durable, igneous rocks are used for tools and building materials.

CHAPTER 2: MINERALS AND ROCKS 2.4 Sedimentary Rocks

Sedimentary Rocks Sediment is small, solid pieces of material that come from rocks or living things. Processes like weathering, erosion, deposition, compaction, and cementation help form sedimentary rocks.

Sedimentary Rocks Weathering: the breaking apart/wearing down of materials. Erosion: the movement of sediment Deposition: the depositing, or laying down, or sediment. Compaction: the process that presses sediments together. Cementation: the process in which dissolved minerals crystallize and glue sediments together.

Sedimentary Rocks There are three main groups of sedimentary rocks: Clastic rocks Organic rocks Chemical rocks

Clastic Rocks A sedimentary rock formed when rock fragments are squeezed together. Grouped by the size of the rock fragments Examples: shale, sandstone, conglomerate, and breccia.

Organic Rocks Forms where the remains of plants and animals are deposited in layers. Coal forms from swamp plant remains. Limestone forms in the ocean from animals with shells made of calcite.

Chemical Rocks Forms when minerals dissolved in a water solution crystallize. Sometimes these are formed from mineral deposits in seas/lakes that evaporate. Such as halite (rock salt) Limestone is an example of this when calcite is dissolved and crystallizes.

Uses for Sedimentary Rocks Again, many types of sedimentary rocks are used for tools and building.

CHAPTER 2: MINERALS AND ROCKS 2.5 Metamorphic Rocks

Metamorphic Rocks Any rock that forms from another rock as a result of changes in heat or pressure or both is called metamorphic.

Classifying Meta. Rocks Foliated Rocks: When grains are arranged in parallel layers or bands in the rock. Slate is an example; formed from shale.

Classifying Meta. Rocks Non-foliated Rocks: The grains in these rocks are arranged randomly. Quartzite forms from quartzite sandstone. Marble forms from limestone.

Using Meta. Rocks Marble is great for sculpting into different shapes, so it is used in statues and buildings. Slate is also used in many building structures because it splits into layers easily.

CHAPTER 2: MINERALS AND ROCKS 2.6 The Rock Cycle

The Rock Cycle Series of processes that occur in and on Earth to slowly change rocks from one kind to another. There is no set pathway for rocks to follow.

The Rock Cycle The changes that rocks go through are related to plate tectonic activity. Plate movement helps to form and move magma, mountains, and other structures. Materials are not lost during the change, they are just transformed.

The Rock Cycle