Minerals Overview

Minerals

• Minerals are naturally occurring, solid, homogenous, and inorganic.
• Minerals are identified by their chemical composition and physical properties.
• Chemical composition is what a mineral is made of.
• Quartz (SiO2) and Graphite (C) are examples of chemical compositions.
• Physical properties include color, streak, hardness, crystal habit, cleavage, fracture, and luster.
• Hardness is a mineral's resistance to being scratched.
• A mineral can only be scratched by something that is as hard or harder than it is.
• Quartz and Garnet both have a hardness of 7 and are often used as abrasives.
• Luster describes how light reflects off a mineral.
• Metallic minerals have a shiny, reflective surface and reflect all light.
• Non-metallic minerals have a duller surface.
• Crystal Habit is the shape a mineral takes when it forms in ideal conditions.
• Halite (table salt) forms in cubes.
• Calcite forms in rhombic shapes.
• Cleavage describes a mineral's tendency to break along smooth, flat planes.
• Mica and biotite have a flat and sheet-like cleavage.
• Fracture describes the way a mineral breaks irregularly.
• Quartz and pyrite typically fracture.
• Diamond and Graphite are both composed of carbon (C) but have different physical properties due to their internal atomic structures.
• Silicon (Si) and Oxygen (O) are the most abundant elements in the Earth's crust and are found in many common minerals, including the 12 common minerals that make up most rocks.
• Silicates are a group of minerals composed of silicon and oxygen.
• Silicates form a Silicon-Oxygen Tetrahedron.
• Quartz and K-feldspar are examples of silicates.

Rocks

• Rocks are classified based on how they are formed.
• Sedimentary rocks are formed by the compaction and cementation of sediments in watery environments.
• Clastic sedimentary rocks are composed of fragments (sediments) like conglomerates, breccia, sandstones, siltstones, and shales.
• Bioclastic sedimentary rocks are formed from once-living organisms.
• Coal is formed from dead plant matter.
• Coquina is a fossil limestone made of calcite shells.
• Crystalline sedimentary rocks are formed from the precipitation and evaporation of minerals.
• Limestone is made up of calcite.
• Rocksalt is made up of halite.
• Rock Gypsum forms from the evaporation of water.
• Fossils are found in sedimentary rocks because organisms are able to leave imprints underwater.
• Grain size in sedimentary rocks ranges from smallest to largest: clay, silt, sand, gravel, pebbles, and boulders.
• Igneous rocks are formed from the solidification of magma or lava.
• Extrusive or volcanic rocks form outside a volcano or volcanic environment and cool faster.
• Extrusive rocks have a finer grain size (basalt) or a glassy texture (obsidian).
• Extrusive rocks can be vesicular (containing gas pockets) like pumice.
• Intrusive or plutonic rocks form inside the Earth where magma cools slowly over long periods.
• Intrusive rocks are characterized by a coarser grain size (larger crystals) like granite and pegmatites (very large crystals).
• Chemical compositions of igneous rocks:
  • Felsic rocks are light in color and have a higher percentage of aluminum (Al) and silicon (Si). Felsic rocks are less dense than mafic rocks.
  • Mafic rocks are dark in color and have a higher percentage of iron (Fe) and magnesium (Mg). Mafic rocks are denser than felsic rocks.
  • Intermediate rocks are a mix of felsic and mafic minerals.
• Metamorphic rocks are formed from the transformation of existing rocks due to increased temperature and pressure.
• Recrystallization happens when new minerals form or existing crystals grow larger.
• Regional Metamorphism occurs at great depths where temperatures and pressures are very high.
  • Foliation develops in regional metamorphic rocks.
  • Gneiss is a metamorphic rock that displays banding, a type of foliation.
• Contact Metamorphism occurs when existing rocks come into contact with igneous intrusions.
  • Temperature is the primary factor in contact metamorphism.
  • Metamorphic Grade indicates the intensity of metamorphism (higher temperature and pressure).
• The metamorphic grade series can change over time:
  • Shale (sedimentary) Slate Phyllite Schist Gneiss

This quiz covers the basic characteristics and properties of minerals, including their chemical composition and physical attributes. Learn about hardness, luster, crystal habit, and examples of common minerals like Quartz and Graphite. Test your knowledge on how minerals are identified and classified.