The Rock Cycle

Minerals A natural occurring solid with a crystalline structure. Nonliving. Quartz, diamond, and salts are all minerals. Used in jewelry.

Mineral Properties Color: Minerals come in a rainbow of colors. Streak: The color of the powder left behind when you rub a mineral against a rough white tile. It does not vary. Luster: The way a mineral reflects light. Many minerals have a metallic luster.

Mineral Hardness A mineral’s ability to resist being scratched. Some minerals can not be scratched by anything. The softest mineral is talc and is classified by a ‘1.’ The hardest minerals are diamonds and they are classified by a ’10.’

Detecting Hardness Hardness is determined using the Mohs’ scale. The scale goes from 1 to 10. Any mineral that is higher on the scale can scratch any mineral lower on the scale.

Example Suppose you have a mineral whose hardness is unknown. A steel nail (hardness of 5.5) can not scratch the mineral, but a piece of quartz (hardness of 7) can. What is the hardness of this mineral?

Answer Suppose you have a mineral whose hardness is unknown. A steel nail (hardness of 5.5) can not scratch the mineral, but a piece of quartz (hardness of 7) can. What is the hardness of this mineral? The mineral has a hardness between 5.5 and 7 since a steel nail could not scratch it but a quartz could.

Special Properties Magnetism Fluorescence An Electrical Charge Produces a double image

Rocks A natural solid made of one or more minerals. Mountains, valleys, hills, beaches, and the ocean floor are made of rocks.

Igneous Rocks Rock that forms when melted rock cools and hardens. Can form underground or on the Earth’s surface. When formed underground igneous rocks have large crystals. When formed on Earth’s surface they have small or no crystals.

Sedimentary Rocks Pieces of sediment that have been pressed and cemented together. Pieces of sediment settle out of water or wind during deposition. This leads to the formation of sedimentary rocks. Forms from any worn down rock.

Metamorphic Rocks Rock changed by heat and pressure. Can form from any other rock. Found in every mountain range on Earth. Found in the ocean and near some volcanoes.

Examples Draw a line to match. Igneous Rocks Sedimentary Rocks Metamorphic Rocks

How Rocks are Used A natural resource. Sandpaper. Buildings. Monuments. The US Capitol building uses sandstone and marble.

Processes that Change Rocks Weathering is a process of breaking down rocks into sediment. All rocks on the Earth’s surface are weathered. Wind and water also weathers rocks. The process of wearing away and removing sediment by wind, water, or ice is called erosion.

The Rock Cycle A continuous process in which one type of rock changes into another. Weathering, erosion, deposition, heat, and pressure can all change rocks.

Science Up Close Earth recycles rocks through the rock cycle. Heat and pressure can change one type of rock to another.

Soil Formation Soil can be formed from weathered rock under it or from eroded sediment carried from far away. Soil contains minerals. Most soil is made up of more than just weathered rock. Farm soil contains small pieces of decayed plants and animals called humus.

Summary The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock.

Questions What are minerals? What are three visible properties of minerals? How can you determine a mineral’s hardness? How do rocks form? How are rocks changed?