Minerals & Rocks

Minerals A naturally formed, inorganic solid with crystal structure and definate chemical composition. The substance was not formed by or from living things such as plants or animals Made from Chemical elements or compounds Minerals can be identified by their physical and chemical properties Luster, Streak, Crystal, Hardness, Density and Structure.

Luster The way a mineral reflects light Metallic Luster hard, shiny Nonmetallic Luster shiny, glassy, waxy, pearly, earthy (dull)

Streak The streak is the color of the mineral in powdered form. The streak is found by rubbing a fresh corner of the mineral across a white, unglazed streak plate Some metallic minerals leave behind a powder that is not the same color as the mineral. The color of the mineral is not always the same as the streak! Streak is more reliable.

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

Hardness A measure of how easily a mineral can be scratched. Minerals can be tested by scratching the unknown mineral with the edge or point of other materials of known harness

Mohs Scale of Hardness

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

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