Minerals, Rocks and Resources

Minerals Natural substances that are inorganic. The substance was not formed by or from living things such as plants or animals. Chemical elements or compounds. Minerals can be identified by their physical and chemical properties. Color, Luster, Streak, Hardness, Breakage, Specific Gravity (Density), Structure, and Cleavage.

Luster The way light is reflected from a cut surface of a mineral. Metallic Luster hard, shiny Nonmetallic Luster shiny, glassy, waxy, pearly, earthy (dull)

Streak Rubbing a fresh corner of the mineral across a white, unglazed streak plate. The streak is the powdered form of the mineral. Some metallic minerals leave behind a powder that is not the same color as the mineral.

Crystal Structure A regularly shaped solid formed by an ordered pattern of atoms. Examples include: Six sided, cubic, rectangular, sheets, fibers.

Hardness Minerals can be tested by scratching the unknown mineral with the edge or point of other minerals of known harness.

Mohs Scale of Hardness

Cleavage If a mineral breaks along a flat surface, it shows cleavage (to cut, or cleave). Many minerals break along cleavage planes, sometimes parallel to the sides of crystals. Those that break along even surfaces that do not follow the crystal arrangement are said to fracture.

Density Can be found by either dividing the mass of a sample by its volume or flotation. Water’s density is 1 g/cm3 A substance will sink in water if it is more dense and float if it is less dense. Specific Gravity is a ratio of the density of a substance to the density of water.

Rocks Nearly all rocks are composed of one or more minerals. Geologists classify rocks according to how they were formed. Igneous rocks form from lava when it reaches the surface, cools and solidifies. Sedimentary rocks result from the compaction and cementing of layers of sediment. Metamorphic rocks form when other types of rocks are changed by heat and/or pressure.

Igneous Rocks The result of the solidification of magma or lava. Most lack layering, however successive lava flows can form a layered rock structure. Those that cool slowly, deep within Earth, are composed of large crystals. Those that cool faster, at or near the Earth’s surface, have smaller or no visible crystals.

Igneous Rock Formation

Igneous Rock Classification

Sedimentary Rocks Most are composed of the weathered remains of other rocks. Usually are formed by the compression and cementing of particles of sediment. Generally exist as a thin layer over metamorphic and igneous rocks.

Sedimentary Rock Characteristics Fragmental rocks are made up of different sized particles such as shale, sandstone and conglomerate (composed of pebbles or larger stones held together by natural cement). Organic sedimentary rock contain the accumulation of plant and animal remains. Fossils are commonly found. Chemical sedimentary rocks are deposited by the settling of materials from solution in seawater. This occurs during the evaporation of seawater and when chemical reactions in the water form compounds that settle. Rock Salt is an example.

Sedimentary Rock Classification

Metamorphic Rocks Form when sedimentary and igneous rocks are changed by heat and/or pressure. The only kind of rock that forms directly from another rock. Metamorphism may cause structures, such as layering, to become distorted or to disappear. It also may cause new minerals to form, and/or crystals to grow. Most are formed deep within the Earth and pushed to the surface when mountains are formed.

Metamorphic Rock Classification Texture Appearance and feel of the rock surface Grain Size Composition Type of Metamorphism

Metamorphic Rock Classification

The Rock Cycle Natural changes in rocks and rock material that takes place at the Earth’s surface and within Earth. Nearly all rocks are made from the remains of other rocks. Rocks are classified based of their origin. Rocks can change in response to changing conditions at the surface or within Earth.

The Rock Cycle

Natural Resources Substances from the Earth. Renewable resources can be replaced after they have been used. trees, fresh water, wind Nonrenewable resources cannot be replenished after they are used for millions of years, if at all. Metals - gold, copper, iron, Fossil Fuels – coal, oil and natural gas

Alternative Energy Sources Solar energy can be used to provide heat, hot water and generate electricity. However, the amount of solar energy that reaches Earth varies with the time of day and the seasons. Geothermal energy, heat from within Earth, can be used but is available only in certain areas around the world.

Alternative Energy Sources Wind-driven generators are used in many areas to provide electricity where there are strong, steady winds. Nuclear energy can generate electricity without pollution. However, there is a danger of a nuclear accident and long-term storage of radioactive wastes.