Earth's Materials: Minerals and Rocks

Earth's Materials: Minerals and Rocks

• Minerals and rocks make up the materials of the Earth.

Elements and Atoms

• An element is made of the same kind of atoms and cannot be broken down by a chemical reaction.
• An atom is the smallest particle of matter that maintains the chemical properties of an element.
• Atomic structure consists of a central nucleus of protons and neutrons, surrounded by orbiting electrons.
• Protons are dense particles with a positive electrical charge.
• Neutrons are dense particles with no electrical charge.
• Electrons are dense particles with a negative electrical charge.
• Orbitals define the path an electron takes around the nucleus.
• Every element has a specific number of protons in its nucleus which defines its atomic number.
• In an electrically neutral atom, the number of protons equals the number of electrons.
• An element is essentially a large collection of electrically neutral atoms, all having the same atomic number.
• Atomic Mass equals the number of protons plus the number of neutrons in an atom.
• Isotopes are atoms of the same element with the same atomic number, but different atomic masses due to varying numbers of neutrons.
• Atomic Weight calculates by adding the atomic masses of the isotopes of an element, it is weighed by the isotope´s relative abundance.
• The periodic table organizes elements by atomic number, showing periodic trends and grouping elements with similar properties.
• Almost 99% of the Earth's crust consists of just eight elements.
• Oxygen makes up 46%.
• Silicon accounts for 28%.
• Aluminum comprises 8%.
• Iron is 5%.
• Calcium is 4%.
• Sodium accounts for 3%.
• Potassium is 3%.
• Magnesium is 2%.
• All the other elements are minor but necessary additions to make up the final 1%.

Chemical Bonds

• An atom achieves a stable configuration when its outermost electron shell is full.
• Noble gases have complete outer electron shells and are inert.
• Atoms interact by donating, accepting, or sharing electrons to achieve stable configurations.
• A chemical bond is an attraction that links atoms together to reach stability.
• Most elements that have reactive chemicals join to achieve similar neutrality to noble gasses, maintaining overall electrical neutrality.
• A compound occurs when a chemical link joins two or more elements in defined proportions, also commonly known as a "molecule".
• Ionic Bonds result from electrostatic attraction between a cation and an anion. Created by electrons transferring from one atom to another.
• When a neutral sodium atom (11 protons/11 electrons) loses an electron, it becomes a positively charged ion (11 protons/10 electrons).
• Similarly, when a neutral chlorine atom (17 protons/17 electrons) gains an electron, it becomes a negatively charged ion (17 protons/18 electrons).
• Covalent Bonds form when two atoms share valence electrons, often involving the overlapping of their orbitals. Typically occurs when atoms share negative charges.
• Minerals such as silicates from covalent bonds easily.
• If the atoms joined have differing quantities of the atoms that are electronegative, the electron density tends to concentrate around the more electronegative atom, leading to a polar covalent bond and creating an electric dipole.
• Metallic Bonds involve valence electrons moving freely between ions. Found in metals like copper, gold, aluminum, and silver. Responsible for the electrical conductivity and malleability of metals.

Minerals

• Mineralogy centers around studying a mineral's traits, formation, makeup, and how it is distributed.
• A mineral is a naturally occurring, inorganic, solid substance with an ordered crystalline structure and a defined chemical composition.
• For a substance to be considered a mineral it has to be a solid matter.
• All mineral solids are found within temperature intervals within ground Earth´s surface.
• Minerals, normally formed through being inorganic, meaning they form salts.
• Minerals may be compounds, their composition typically represented by chemical formulas. Atomic substitution within the crystal structure allows for composition variance within certain limits, without altering the properties of these minerals.
• Atoms are arranged in an ordered and repetitive model with regular shapes known as crystals.
• Minerals like obsidian and opal are mineraloids because they lack a crystalized formation. Mineraloids are typically made of amorphous matter, such as glass.

Physical properties of minerals

• The physical properties of minerals includes; shape, magnetism, specific weight, cleavage and fracture, hardness, stripe, brightness or luster, and color.

Crystalline Form and Habit

• Habit describes the typical shape. It represents the arrangement of a crystal, and the internal structure.
• Acicular crystals are thin and needle-like.
• Prismatic/Columnar crystals are shaped like prisms.
• Laminar/Foliated crystals form in layers or sheets.
• Tabular crystals are elongated and in the shape of slabs.
• Dendritic crystals display a branched, or tree-like structure.
• Radial crystals grow outward from a central point.
• Drusy surfaces are covered with crystals.
• Fibrous minerals appear as aggregates of fine parallel fibers.
• Massive minerals are compact and irregular in shape.
• Botryoidal minerals have a globular, grape-like structure.

Cleavage, Fracture, and Transparency

• Cleavage describes how a mineral will break apart at the seams, known as the "planes of weakness".
• Fracture describes the irregular breaking of a mineral when it does not cleave.
• Transparency defines how clearly a mineral transmits light and can be listed as either transparent, translucent, or opaque.

Chemical Properties

• Soloubility reflects that some minerals can be dissolved.
• Acid is commonly used in dissolving a mineral for study.
• Effervescence is the release of carbon dioxide that occurs in certain instances.

Mineral Species and Rock-Forming Minerals

• About 6,000 mineral species are recognized by the International Mineralogical Association (IMA).
• Minerals are classified based on their chemical composition.
• Silicates tend to have a crystaline structure.
• Silicates are subdivided based on their arrangement.
• Oxides combine metal and oxygen
• Carbonates contain carbon and oxygen.
• Halides contain a metal and a halogen.
• Sulfides have a combination of sulfur and other elements.
• Sulfates contain sulfur and oxygen.
• Phosphates contain phosphorus.
• Native elements are in their simplest form.

Silicates

• Silicates are the most abundant class comprising of the Earth's crust due to oxygen and silicon being readily available.
• Silicates are formed by
  • Melted rock cooling (quartz)
  • Weathered silicats (clay)
  • Mountain creation because of high-pressure.
• The two kinds are as follows
  • Ferromagnesians (dark) -Nonferromagnesians (clear)

Other mineral families

• Oxides: Formed from metals and oxygen
• Carbonates: Formed from carbon and Oxygen
• Halides: Combination of metal and a halogen
• Sulfides: Combination of sulphur and other elements
• Sulfates: Combination of sulfur and oxygen
• Phosphate Elements

Mineral Structures and Crystal Systems

• Mineral atomic structure was discovered to have crystal formations by the use of x-rays around 1912.
• The most basic of crystal formations is the cell unit.
• The arrangement of cell units is the cause of mineral group differences.
• A total of seven primary structures exist in crystalline systems.

Rocks

• Rocks are combinations of minerals that have defined textures, that were formed because of a geologic process, and tell us about geologic history.
• The three types of rocks that make up Earth are:
  • Igneous
  • Sedimentary
  • Metamorphic Metamorphism occurs if it is put under a different pressure and temperature than normal.

Rock cycle

• Magma causes a molten rock to erupt on the crust or surface, which makes an igneous rock.
• Weathering by wind causes this to change, becoming sediment.
• Pressure and composition turns it into sedimentary stone.
• Metamorphism occurs, and the rock becomes metamorphic.
• Melting, or Fussion occurs. Which turns it into magma. Which causes a new process. This is the rock cycle.