Mineral Identification and Formation

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Questions and Answers

Why is the traditional definition of a mineral problematic?

  • It relies on outdated concepts of atomic structure and chemical bonding.
  • It includes substances like water and mercury that do not meet all the criteria. (correct)
  • It excludes substances like coal and obsidian, which are important geological resources.
  • It is too broad and includes organic materials like pearls and clam shells.

According to the International Mineralogical Association's definition, when is calcite in a clam shell considered a mineral?

  • When the calcite comprises more than 50% of the clam shell's mass.
  • When the clam is still alive and the shell is actively growing.
  • When the clam shell undergoes burial, diagenesis, or other geological processes. (correct)
  • When the calcite exhibits a particularly well-formed crystal structure.

What is the primary difference between a mineral and a rock?

  • A mineral is formed by geological processes, while a rock is formed by biological processes.
  • A mineral is organic, while a rock is inorganic.
  • A mineral has a defined chemical composition, while a rock is composed of one or more minerals or mineraloids. (correct)
  • A mineral is a naturally occurring solid, while a rock can be a liquid or gas.

Which of the following substances would be classified as a mineraloid?

<p>Opal, due to its amorphous structure. (A)</p> Signup and view all the answers

What are the three main types of rocks based on their formation processes?

<p>Igneous, sedimentary, and metamorphic. (D)</p> Signup and view all the answers

Which of the following statements about isotopes is most accurate?

<p>Isotopes of an element have the same number of protons but a different number of neutrons. (A)</p> Signup and view all the answers

What determines the chemical properties of an element?

<p>The number of electrons in the valence shell. (B)</p> Signup and view all the answers

What is the significance of columns in the periodic table in relation to the elements' electron configuration?

<p>Elements within the same column have the same number of electrons in their valence shells, leading to similar chemical characteristics. (C)</p> Signup and view all the answers

The mineral olivine has the chemical formula $(Mg, Fe)_2SiO_4$. What does the comma between iron (Fe) and magnesium (Mg) indicate?

<p>Iron and magnesium can substitute for each other in the crystal structure. (A)</p> Signup and view all the answers

Which of the following reflects the appropriate relationship between atomic number, protons, and neutrons?

<p>The atomic number is the number of protons in the nucleus. (D)</p> Signup and view all the answers

Which of the following describes the process of mineral formation in the Great Salt Lake, Utah?

<p>Minerals precipitate due to the evaporation of water, leading to increased salt concentration. (D)</p> Signup and view all the answers

What distinguishes aragonite from calcite?

<p>Aragonite and calcite have same chemical formula but different crystal structures. (B)</p> Signup and view all the answers

How does the silicon-oxygen tetrahedron contribute to the formation of silicate minerals?

<p>It acts as a negatively charged molecule that bonds with positively charged ions. (D)</p> Signup and view all the answers

Identify the correct chemical formula for olivine, a rock-forming mineral often found in Earth's mantle.

<p>($Fe, Mg)_2SiO_4$ (A)</p> Signup and view all the answers

Which of the following best describes a 'solid solution' in the context of mineral composition?

<p>Two or more elements with similar properties that can substitute for each other within a crystal structure. (C)</p> Signup and view all the answers

Which of the following statements correctly describes the behavior of elements in group VII (column 17) of the periodic table when forming chemical bonds?

<p>They readily take up one electron to achieve a stable electron configuration, becoming negatively charged anions. (C)</p> Signup and view all the answers

What type of bonding is most likely to occur between calcium (Ca), a metal from group II, and oxygen (O), a nonmetal from group VI?

<p>Ionic bonding, characterized by the transfer of electrons from calcium to oxygen, forming ions that are electrostatically attracted together. (A)</p> Signup and view all the answers

An element is found to have 7 electrons in its valence shell. Which of the following is most likely to be true about this element?

<p>It will readily gain 1 electron to form an anion with a -1 charge. (A)</p> Signup and view all the answers

What is the primary factor that determines whether a mineral precipitates directly from an aqueous solution?

<p>The concentration of ions in the solution, temperature, and pressure. (B)</p> Signup and view all the answers

What characteristic defines noble gasses?

<p>Noble gasses possess full valence shells, making them chemically inert. (A)</p> Signup and view all the answers

Flashcards

Selenite Crystals

Large gypsum crystals found in The Cave of the Crystals

Mineral Definition

A mineral is naturally occurring, inorganic, solid, crystalline, with a defined chemical composition.

Mineraloids

Substances like coal and opal that don't fit the mineral definition.

Types of Rocks

Rocks are classified as igneous, sedimentary, and metamorphic based on formation processes.

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Atom Composition

Atoms are made of protons, neutrons, and electrons, the basic units of matter.

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Atomic Number

The number of protons in an atom's nucleus.

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Periodic Table

A tabular arrangement of elements by atomic number.

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Isotope

Atoms of the same element with different neutron counts.

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Chemical Bonding

The process by which atoms combine to form compounds.

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Valence Shell

The outermost shell of an atom where electrons interact in bonding.

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Sodium Ionic Charge

Sodium has an overall net charge of +1 when it loses one valence electron.

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Cations

Positively charged ions that lose electrons, attracted to cathodes.

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Anions

Negatively charged ions that gain electrons, attracted to anodes.

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Ionic Bonds

Chemical bonds formed by the electrostatic attraction between oppositely charged ions.

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Precipitation

The process in which ions in solution form solid minerals, often dependent on temperature and concentration.

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Travertine

A natural limestone formed by calcite precipitation in warm springs.

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Silicon-Oxygen Tetrahedron

A molecular ion central to the structure of silicate minerals, consisting of one silicon atom and four oxygen atoms.

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Calcite

A common mineral composed of calcium carbonate (CaCO3), often formed biologically by organisms.

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Olivine

A green mineral primarily found in the Earth's mantle, with a formula of (Fe, Mg)2SiO4, known for solid solution properties.

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Biogenic Sediments

Sediments formed from the accumulation of hard parts of organisms after they die, like bones or shells.

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Study Notes

Mineral Identification and Formation

  • Definition of a Mineral (Geological Sense):
    • Naturally occurring
    • Inorganic
    • Solid at room temperature
    • Regular crystal structure
    • Defined chemical composition
  • Modified Definition (International Mineralogical Association):
    • Element or chemical compound
    • Normally crystalline
    • Formed through geological processes
  • Mineraloids: Substances not fitting the mineral definition (e.g., coal, pearl, opal)
  • Rock Composition: Composed of one or more minerals (or mineraloids)
  • Rock Types:
    • Igneous: Crystallize from molten material
    • Sedimentary: Formed from products of weathering (mechanical & chemical)
    • Metamorphic: Altered rocks by heat & pressure

Mineral Chemistry

  • Matter Composition: Atoms composed of protons, neutrons, and electrons.
  • Atomic Structure:
    • Nucleus: Protons (+ charge), Neutrons (no charge) Electrons (- charge)
    • Electron shells; valence shell (outermost)
  • Elements & Atomic Number: Atoms with a specific number of protons
  • Isotopes: Forms of an element with the same number of protons but different numbers of neutrons.
  • Atomic Mass: Average mass of atoms in nature (often not a whole number).
  • Periodic Table: Arrangement of elements by atomic number, with symbols, names, atomic numbers, and atomic masses.

Chemical Bonding

  • Compounds & Molecules: Formed by chemical bonds; covalent (sharing electrons), ionic (transferring electrons).
  • Ionic Bonds: Attraction between ions with opposite charges (metal & nonmetal)
  • Covalent Bonds: Sharing of electrons between nonmetal atoms
  • Ions: Atom with a net positive or negative charge (cations +, anions -)
  • Octet Rule: Atoms tend to gain or lose electrons to achieve a full outer electron shell
  • Noble Gases: Chemically inert as their valence shells are full
  • Transition Metals: Elements in the center of the periodic table, varying oxidation states, affect rock colors (e.g., Fe+2 to Fe+3).

Mineral Formation

  • Precipitation: Ions in solution come together to form minerals, often dependent on concentration, temperature, and pressure
  • Crystallization: Formation of minerals from magma as it cools
  • Biological Precipitation: Organisms extract ions from water and precipitate minerals (e.g., calcite in shells, bones)

Mineral Classification

  • Silicate Minerals: Largest group, based on silicon-oxygen tetrahedron, which bonds and forms various structures (isolated, chains, sheets, 3D)

  • Iron/Magnesium substitution in Olivine Series: Example of Solid Solutions

    • Olivine: Fe, Mg, substitution in the solid state
    • Fayalite (pure Fe) and Forsterite (pure Mg) as end members

  • Other Mineral Families:

    • Pyroxenes: Polymerized single chains of silica tetrahedra.
    • Amphiboles: Polymerized double chains of silica tetrahedra
    • Sheet silicates (phyllosilicates): Mica and clay minerals, bonded in sheets.
    • Framework silicates (tectosilicates): Quartz and Feldspars; 3-dimensional framework of silica tetrahedra

  • Non-Silicate Minerals: Not based on silica tetrahedra, important economically for metals, construction materials, etc.

  • Carbonates: Calcium carbonate (calcite) , dolomite (most common)

    • Formation & tests for calcite/dolomite identification

  • Oxides: Metal ions bonded to oxygen (e.g., iron oxides, rust)

  • Halides: Halogens bonded with other ions (e.g., halite, sylvite)

  • Sulfides: Metals bonded to sulfur (e.g., galena, sphalerite)

  • Sulfates: Metal ions bonded to sulfate ions, (e.g., gypsum)

  • Phosphates: Phosphate unit (PO4-3) with other ions and atoms (e.g., apatite)

  • Native Elements: Minerals composed of a single element (e.g., gold, carbon).

Identifying Minerals

  • Physical Properties: Used in field and lab settings.
    • Luster & Color: Appearance
    • Streak: Color of powdered mineral
    • Hardness: Scratch resistance (Mohs Hardness Scale)
    • Crystal Habit: Shape of crystals
    • Cleavage & Fracture: Way mineral breaks
    • Special Properties: Taste, magnetism, fluorescence, birefringence, etc.
  • Cleavage and Fracture: Identifying minerals based on breakage patterns
  • Twinning: Creating parallel mirror images in crystals, creating striations.
  • Solid Solutions: Formation of series of minerals based on varying elements in a structure
  • Specific Gravity/heft: Subjective relative weight compared to water
  • Acid test: Solution to identify calcite and dolomite
  • Fluorescence & Phosphorescence: Optical properties that react to UV radiation or black light

Summary

  • Minerals are the building blocks of rocks.
  • Formed by various geologic processes.
  • Identified by unique physical properties which are derived from atomic structure and bonding.

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