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Minerals, Rocks and Rock Cycle - Vocabulary Flashcards (ENGLISH)

Minerals

  • Definition of minerals
    • Naturally occurring in nature
    • Solid
    • Inorganic (not a product of living tissue)
    • Definite chemical composition (unique chemical composition)
    • Crystalline structure (atoms arranged in orderly patterns)
    • Example: NaCl (Halite)
  • Special examples/exceptions
    • Naturally occurring ice is a mineral; man-made ice and water are not minerals
    • Amber (C{10}H{16}O) is not a mineral
    • Magnetite (Fe{3}O{4}) formed by certain bacteria is a mineral

Question 1: Which of the following substances is not considered a mineral?

  • A. coal • B. diamond • C. gypsum • D. rock

Atomic composition and occurrence

  • An atom is a fundamental form of matter that cannot be broken into simpler substances by ordinary chemical processes.
  • A total of 88 elements out of 118 identified occur naturally in the Earth’s crust.
  • Only the 8 most abundant elements make up 98.59\% of the Earth’s crust.

Composition of Minerals

  • The Earth’s crust is built from a limited set of elements, with trace amounts of many others contributing to mineral diversity.

Structure of the atom

  • An atom consists of a positively charged nucleus and a cloud of negatively charged electrons.
  • The nucleus is made up of neutrons and positively charged protons.

Question 2: Melting of minerals breaks chemical bonds; which bond is the strongest?

  • A. ionic • B. covalent • C. metallic • D. Van der Waals

Chemical bonds in minerals

  • Cations are positively charged; anions are negatively charged.
  • Atoms or ions are held together by chemical bonds in definite proportions to form minerals.
  • Types of chemical bonds:
    • Ionic bond: formed when one or more electrons are removed from one atom and attached to another.
    • Covalent bond: formed when one or more pairs of electrons are shared by two atoms (strongest).
    • Metallic bond: some electrons are loose and not associated with a particular atom.
    • Van der Waals bond: a weak type of bond that does not share or transfer electrons.

Crystal structure and the nature of crystals

  • Crystalline structure: Atoms in a mineral are specifically ordered based on atomic patterns.
  • Glass: a solid with disordered atoms.
  • A crystal is a single, continuous piece of a crystalline solid.
  • Crystal faces: flat surfaces of a crystal grown without obstructions.
  • Law of constancy of interfacial angles: angles between the same faces on crystals of the same substance are equal.
  • Regular, orderly, and periodically repeated arrangement of atoms constitutes the crystal structure of a mineral.

Question 2 (revisited): Boldest bonds

  • The strongest chemical bond is covalent.

Polymorphs

  • Polymorphs: minerals with the same chemical composition but different crystal structures.
  • Conditions such as temperature (T) and pressure (P) determine the crystal structure.

Question 3: Aragonite (density \rho=2.9\ \text{g/cm}^3) has the same chemical composition as calcite (\rho=2.7\ \text{g/cm}^3). Which is more likely formed under high pressure?

  • Answer: Aragonite

Mineral formation

  • Crystallization from melt (igneous rocks)
  • Precipitation from water (chemical sedimentary rocks, hydrothermal ore deposits)
  • Biological activity (biochemical sedimentary rocks)
  • Change to a more stable state (weathering, metamorphism, diagenesis)
  • Precipitation from vapor (not common, but can occur around volcanic vents)

Crystal growth

  • Crystals grow as atoms bond to mineral surfaces starting from a central seed.
  • Growth expands outward as atoms accumulate.
  • Modes of growth:
    • Solidification from a melt
    • Precipitation from solution
    • Solid-state diffusion
  • Larger crystals require longer growth time.

Question 4: Quartz can be formed by cooling of felsic magma. The quartz crystals will be large for:

  • A. slowly cooling magma • B. fast cooling magma • C. magma cooled under water • D. magma cooled in the air

Physical properties of minerals (identification)

  • Properties depend on chemical composition and crystal structure (bonding).
  • Some properties are diagnostic; each mineral has a unique set of physical properties.

Colors & examples

  • Color: color or color range as seen in reflected light.
    • Quartz: colorless, white, pink, purple, brown, green, blue (range of colors).
    • Pyrite: typically gold in color.
    • Corundum: ruby and sapphire varieties.

Streak

  • Color of a mineral in powdered form.
  • Streak may differ from the mineral’s bulk color.
  • Hematite: may be silver/gray in bulk but leaves a reddish-brown streak.
  • Pyrite: gold in bulk but leaves a black streak.

Luster

  • How a mineral’s surface reflects light:
    • Metallic vs non-metallic.
    • Non-metallic subtypes: Vitreous (glassy), Satiny, Silky, Resinous, Pearly, Earthy (dull), Adamantine (brilliant).

Hardness

  • Resistance to scratching.
  • Mohs hardness scale (reference set).
  • Tests can use common objects (fingernail, copper penny, nail, glass).

Specific Gravity

  • How heavy a mineral is for its size; defined as mass divided by volume.
  • Example comparison: Pyrite vs Calcite.
  • \text{Specific Gravity} = \frac{\text{mass}}{\text{volume}}

Crystal habit

  • The ideal shape of crystal faces.
  • Related to the structural arrangement of atoms.
  • Requires ideal growth conditions.
  • Common forms: cubes, blades, hexagonal prisms, dodecahedra, rhombohedra, octahedra; compound forms like tetragonal prisms.

Cleavage

  • Tendency to break along flat surfaces (planes of weakness in crystal structure).
  • Produces flat, shiny surfaces.
  • The number of cleavage planes and the angles between them aid identification (e.g., amphibole, feldspar, mica).

Fracture

  • Irregular breakage.
  • Some minerals lack planes of lattice weakness and thus do not cleave; they fracture.
  • Conchoidal fracture: typical of quartz and obsidian.

Other properties

  • Magnetism (e.g., magnetite)
  • Reaction to acid (e.g., calcite, dolomite)
  • Taste (e.g., halite)
  • Flexibility (e.g., gypsum – flexible in thin sheets)
  • Feel (e.g., talc)

Question 5: Describe a strategy to prove that an unknown clear calcite crystal is not the same mineral as a known clear crystal of quartz.

Mineral classification by anions

  • Minerals are commonly classified by their anions:
    • Oxides (e.g., magnetite, hematite)
    • Silicates (e.g., olivine, pyroxene)
    • Carbonates (e.g., calcite, dolomite)
    • Sulfides (e.g., pyrite, galena)
    • Halides (e.g., halite, fluorite)
    • Native elements (e.g., gold, copper, diamond)

Major groups of minerals and the silicate framework

  • Silicates – contain ext{SiO}_4^{4-} (e.g., quartz, feldspar, olivine; pyroxene, mica)
  • Carbonates – contain ext{CO}3^{2-} (e.g., calcite, aragonite, dolomite – ext{CaCO}3)
  • Sulfates – contain ext{SO}4^{2-} (e.g., gypsum – ext{CaSO}4\cdot 2\text{H}_2 ext{O})
  • Sulfides – contain ext{S}^{2-} (no O) (e.g., pyrite – ext{FeS}_2; galena – ext{PbS})
  • Phosphates – contain ext{PO}4^{3-} (e.g., apatite, ext{Ca}10( ext{PO}4)6( ext{OH, F, Cl})_2)
  • Oxides – contain ext{O}^{2-} but not bonded to Si, C, or S (e.g., hematite – ext{Fe}2 ext{O}3; magnetite – ext{Fe}3 ext{O}4)
  • Halide – contain ext{Cl}^{-} or ext{F}^{-} (e.g., halite – ext{NaCl}; fluorite – ext{CaF}_2)
  • Native elements – composed entirely of one element (e.g., diamond – ext{C}; gold – ext{Au})

Silicate minerals and the crystal structure families

  • Silicate minerals dominate Earth’s crust and are known as the rock-forming minerals.
  • Silica tetrahedron: ext{SiO}_4^{4-}; 4 oxygen atoms bonded to 1 silicon atom.
  • Silica tetrahedra link together by sharing oxygen.

Silicate structures (family overview)

  • Independent tetrahedron: no oxygen sharing; linked by cations (e.g., olivine).
  • Single-chain silicates: chains bonded with Fe and Mg (e.g., pyroxene).
  • Double-chain silicates: varied cations (e.g., amphibole).
  • Sheet silicates: two-dimensional sheets of linked tetrahedra (e.g., mica, clay minerals like muscovite).
  • Framework silicates: all four oxygens are shared; includes feldspar and quartz (SiO$_2$-group).

Rocks and the rock cycle

  • Rocks definition: a coherent naturally occurring solid, consisting of an aggregate of minerals or a mass of glass.
  • Clastic rocks: grains cemented together.
  • Crystalline rocks: crystals interlock with one another.
  • Three basic rock types: igneous, sedimentary, metamorphic.

The Rock Cycle

  • A series of processes that causes rock to change from one type to another, driven by plate tectonics and climate interactions.
  • Sedimentary path: Weathering → Transportation → Deposition → Lithification → Sedimentary Rocks.
  • Metamorphic path: Metamorphism → Metamorphic Rocks.
  • Uplift and exposure bring rocks to the surface.
  • Melting produces magma; cooling/crystallization forms Igneous Rocks (extrusive vs. intrusive).
  • Igneous rocks can weather to form sedimentary rocks, or be buried and metamorphosed to metamorphic rocks; metamorphic rocks can melt again to start the cycle over.

Diagrammatic flow (conceptual)

  • Weathering and erosion transport material to depositional environments, where lithification forms sedimentary rocks.
  • Subduction and deep burial induce metamorphism; uplift exposes rocks to surface processes.
  • Heating and partial melting produce magma; magma crystallizes to form igneous rocks (intrusive or extrusive).

Take-home messages

  • Know what minerals are and the five defining characteristics.
  • Minerals are organized by properties that reflect differences in chemical composition and bonding.
  • Know the seven diagnostic properties used to identify minerals and the diagnostic properties of common minerals.
  • Understand the silicate tetrahedron and how it creates different silicate structures.
  • Recognize some common groups of minerals besides silicates.
  • Explain how one type of rock transforms into another through the rock cycle.

Connections and key reminders

  • The origin and evolution of the marine environment ties into mineral formation, silicate minerals, and the rock cycle through hydrothermal processes, sedimentation, and tectonic activity.
  • Crystal structure and bonding principles help explain mineral properties like hardness, cleavage, and color.
  • The four major rock types and the cycle provide a framework to understand landscape evolution and resource formation (e.g., ore deposits linked to hydrothermal activity).
  • Practical implications include resource exploration (ore deposits, fossil fuels in sedimentary sequences) and interpretation of geological records.

Quick reference formulas and constants

  • Earth crust elemental composition reference (approximate):
    • 88 elements occur naturally in the crust, out of 118 identified.
    • The 8 most abundant elements make up about 98.59\% of the crust.
  • Silicate tetrahedron: ext{SiO}_4^{4-}
  • Rocks and processes are described in terms of common units (g/cm³ for density; hardness scales; etc.).

Example questions recap (from transcript)

  • Mineral definition questions and examples (ice, amber, magnetite relevance).
  • Bond strength question: covalent > ionic > metallic > van der Waals.
  • Density-based high-pressure inference: higher-density polymorphs often indicate high-pressure formation (e.g., aragonite vs calcite).
  • Crystal growth and cooling rate: slower cooling yields larger crystals (quartz on felsic magma).
  • Proven strategies for mineral identification using multiple diagnostic properties (e.g., calcite vs quartz test).