Minerals and Rocks Chapter 4: Lesson 1

What are Minerals??? Many common substances found on Earth are made of minerals. Mineral- A solid, that is formed in nature and has never been alive. Ex: table salt, gold, and iron.

What are Minerals??? Cont… The graphite in your pencil is a mineral too. Minerals are found underground and in soil. They are even in the ocean. There are more than 3,000 different kinds of minerals. You can tell minerals apart because each mineral has its own properties. There are four physical properties that can help you identify minerals. They are color, streak, luster, and hardness.

COLOR Most minerals come in just one color. However, some, like quartz come in many colors  Some, like gold and pyrite (Fool’s Gold) are the same color  P-G You cannot use color alone to identify a mineral.

Streak Streak is another property used in identifying minerals. Streak- the color of the powder left when a mineral is rubbed across a white tile. A mineral’s streak may or may not be the same as the mineral’s color.

Luster Luster- how light bounces off a mineral. Minerals can be shiny, pearly, or glassy and other minerals are dull. Some minerals are shiny like metal. Mica has a pearly luster. Sulfur has a dull luster. It is yellow.

Hardness The hardness of a mineral describes how easily a mineral can be scratched or can scratch something else. The harder the mineral, the fewer things can scratch it. The hardness is numbered 1-10 with 1 being the softest and 10 being the hardest. Diamond-it is the hardest mineral. It is a 10 on the scale. Some minerals like talc and gypsum, are soft. They can be scratched with a fingernail.

Special Properties If acid (vinegar) is placed on a mineral, it may bubble or fizz. (Calcite and Limestone) Some minerals split into thin sheets. Some minerals are magnetic.

How Can Hardness Be Used to Identify Minerals??? Mineral HardnessColorLusterSpecial Properties Calcite3- Scratched by nail WhiteDull/GlassyBubbles with acid Feldspar6- Scratches glass Pink or WhiteDull/Pearly Mica2- Scratched by fingernail Black/GrayShinySplits into thin sheets Talc1- Easily scratched by fingernail WhiteDull Gypsum2 – Scratched by fingernail White/GrayDull Quartz7- Scratches Glass Various ColorsGlassy Flourite4Various Colors Properties

What are Rocks??? Rock- a nonliving material made of one or more minerals. (Rocks are made up of minerals) Rocks are made of mineral pieces called GRAINS. A rock’s texture is how its grains look. Some rocks have large grains you can easily see. These rocks have coarse texture. (Granite) Rocks whose grains are too small to see have a fine texture. (Basalt)

Three Types of Rocks Rocks are classified by HOW they are formed. There are three types of rocks. 1.Igneous 2.Sedimentary 3.Metamorphic

Igneous Rock Igneous Rock is formed when melted rock cools and hardens. Inside of the Earth, melted rock called magma cools and hardens very slowly. A rock with large grains forms. Granite is an example. Melted rock that flows onto the Earth’s surface is called lava. Lava cools and hardens quickly. A rock with small mineral grains forms. (Basalt forms) Igneous rocks may be glassy or grainy with crystals of different minerals in them.

Sedimentary Rocks Some rocks are formed from sediment. Sediment- tiny bits of weathered rock or once-living animals or plants. Sedimentary Rock- a kind of rock that forms from layers of sediment that have been pressed and cemented together. Ex: Sandstone, shale, and limestone.

Sedimentary Rocks Cont… Sedimentary rocks form where weathered and eroded materials are dropped. This often happens at the bottom of rivers, lakes,and oceans. Over time, sediment piles up. The top layers press on layers below. They squeeze the water and air from the lower layers and press the sediments together. In time the sediment becomes cemented together and forms rock. Some contain fossils or pieces of animal shells, skeletons, or other remains of plants and animals.

Metamorphic Rock Metamorphic Rock- Was once another type of rock deep inside Earth, but heat and the pressing of the rocks above have caused the minerals to change. Deep inside Earth, rocks heat up and “Bake.” They also get squeezed by the weight of the rocks above them. All of this heating and pressure can cause a rock’s minerals to change into new minerals. Ex: Slate and Marble

How do we use minerals and rocks? Eating foods with salt. (mineral-Halite) Telephone wires- made of copper. Jewelry- gold, silver, and iron. Gems- valued for their beauty. People make cement from limestone and burn coal for fuel.

Types of Soil Soil can be classified based on content, texture, or grain size. Types of soil –Humus –Sand –Clay –Silt

Humus Humus- soil that is made up of decayed parts of once-living things. It is dark, soft, and very crumbly.

Sand Sand- has large grains with large spaces between the grains. This lets water leave it quickly. Sand feels gritty.

Clay Clay- has very small grains, much smaller than sand or silt, and holds water easily. Clay is sticky when its wet, but when it dries, it forms hard clumps.

Silt Silt- has pieces smaller than sand. It feels like powder.

Soil Combinations Some soils are combinations of these four types of soil. For example: Loam soil has large and small grains with lots of humus. It is dark and rich. Another example: Potting soil or Topsoil. It also has a lot of humus in it.