Mineralogy and Rock Constituents

Vocabulary flashcards covering key mineralogical concepts, chemical bonding, structural classifications of silicates, and Strunz classes based on the lecture notes.

Mineral

A naturally occurring solid with a defined chemical composition and an ordered, periodic arrangement of atoms forming a crystal structure.

Native Mercury

The only exception to the solid state definition of a mineral at room temperature, existing as a liquid above $-39\,^\text{o}\text{C}$.

Crystal

A solid material whose constituent atoms, molecules, or ions are assembled in an ordered and periodic pattern extending in all three spatial dimensions.

Amorphous Solid

A solid substance that lacks long-range three-dimensional atomic ordering, such as obsidian, opal, or santabarbarite.

Inversion Center

A crystal symmetry operation denoted by $i$ (or $c$) where every point on a crystal structure corresponds to an identical point directly opposite across a central point.

Reflection Plane

A crystal symmetry element, denoted as $m$, representing a mirror plane that divides a crystal into two symmetrical halves.

Rotation Axis

A symmetry axis around which a crystal rotation of $\frac{2\pi}{N}$ reproduces its original appearance, where the allowed rotational order $N$ can only equal 1, 2, 3, 4, or 6.

Polymorphism

The ability of a chemical compound to crystallize into more than one distinct crystal structure depending on pressure and temperature, such as calcite/aragonite or graphite/diamond.

Crystal Twinning

The symmetrical intergrowth of two or more individual crystals of the same mineral species sharing lattice points according to specific crystallographic orientation rules.

Cation

A positively charged atom or molecule formed by losing one or more valence electrons, such as $\text{Na}^+$, $\text{Ca}^{2+}$, or $\text{Fe}^{2+}$.

Anion

A negatively charged atom or molecule formed by gaining one or more valence electrons, such as $\text{F}^-$, $\text{Cl}^-$, or $\text{O}^{2-}$.

Ionic Bond

A chemical bond formed by the complete transfer of valence electrons between atoms, creating oppositely charged ions that attract each other, as seen in $\text{NaCl}$.

Covalent Bond

A strong chemical bond formed by the sharing of electron pairs between adjacent atoms.

Metallic Bond

A non-directional electrostatic attraction between positively charged metallic cations and a surrounding delocalized sea of valence electrons.

Van der Waals Bond

A weak electrical attraction between uncharged, neutral atoms or molecules caused by temporary dipole interactions.

Silicate Tetrahedron

The fundamental structural building block of silicate minerals, consisting of a central silicon cation bonded to four surrounding oxygen anions in a tetrahedral coordination $[\text{SiO}_4]^{4-}$.

Nesosilicates

Silicate minerals featuring isolated $[\text{SiO}_4]^{4-}$ tetrahedra linked exclusively by interstitial cations without sharing oxygens directly between tetrahedra, such as forsterite ($\text{Mg}_2\text{SiO}_4$) and zircon ($\text{ZrSiO}_4$).

Sorosilicates

Silicate minerals characterized by isolated pairs of tetrahedra sharing a single oxygen atom, yielding a basic structural unit of $[\text{Si}_2\text{O}_7]^{6-}$, as seen in akermanite ($\text{Ca}_2\text{MgSi}_2\text{O}_7$).

Cyclosilicates

Silicate minerals in which tetrahedra are linked into closed rings by sharing two oxygen atoms per tetrahedron, with the general unit formula $(\text{Si}_6\text{O}_{18})^{12-}$, such as beryl and tourmaline.

Inosilicates

Silicate minerals whose tetrahedra share oxygens to form single chains (pyroxenes, $(\text{SiO}_3)_n^{2n-}$) or double chains (amphiboles, $[(\text{Si}_4\text{O}_{11})\text{OH}]^{7-}$).

Phyllosilicates

Sheet silicates constructed from continuous 2D sheets of tetrahedra sharing three oxygens, with the formula $[(\text{Si}_4\text{O}_{10})(\text{OH})_2]^{6-}$, including micas, talc, and clay minerals.

Tectosilicates

Framework silicates in which all four oxygens of every $[\text{SiO}_4]^{4-}$ tetrahedron are shared in a 3D network, resulting in a overall neutral base ratio of $\text{SiO}_2$, such as quartz and feldspars.

Strunz Classification

A mineralogical classification system established by Hugo Strunz that divides minerals into 10 primary chemical classes based on composition and crystal structure.

Native Elements

Strunz Class 1 minerals composed of uncombined single chemical elements occurring naturally, divided into metallic (e.g., gold, copper, platinum) and non-metallic types (e.g., sulfur, diamond, graphite).

Sulfides

Strunz Class 2 minerals formed by combinations of the sulfide anion $\text{S}^{2-}$ with metallic cations, including major ore minerals like pyrite ($\text{FeS}_2$), galena ($\text{PbS}$), chalcopyrite ($\text{CuFeS}_2$), and sphalerite ($\text{ZnS}$).

Halides

Strunz Class 3 minerals composed of halogen anions ($\text{F}^-$, $\text{Cl}^-$, $\text{Br}^-$, $\text{I}^-$) bonded with metal cations, such as halite ($\text{NaCl}$), sylvite ($\text{KCl}$), and fluorite ($\text{CaF}_2$).

Oxides and Hydroxides

Strunz Class 4 minerals containing oxygen ($\text{O}^{2-}$) or hydroxyl ($\text{OH}^-$) groups combined with one or more metals, such as corundum ($\text{Al}_2\text{O}_3$), hematite ($\alpha\text{-Fe}_2\text{O}_3$), and magnetite ($\text{Fe}_3\text{O}_4$).

Carbonates

Strunz Class 5 minerals containing the complex anion $[\text{CO}_3]^{2-}$ combined with divalent cations like $\text{Ca}^{2+}$, $\text{Mg}^{2+}$, or $\text{Fe}^{2+}$, including calcite, aragonite, dolomite, and siderite.

Borates

Strunz Class 6 minerals containing trigonal $[\text{BO}_3]^{3-}$ or tetrahedral $[\text{BO}_4]^{5-}$ units that polymerize into complex structures, such as borax and kernite.

Sulfates

Strunz Class 7 minerals built around the sulfate complex anion $[\text{SO}_4]^{2-}$, commonly precipitating in evaporite environments or hydrothermal veins, such as gypsum ($\text{CaSO}_4 \cdot 2\text{H}_2\text{O}$) and barite ($\text{BaSO}_4$).

Phosphates

Strunz Class 8 minerals centered around the phosphate complex anion $[\text{PO}_4]^{3-}$, such as apatite ($\text{Ca}_5(\text{PO}_4)_3(\text{OH},\text{Cl},\text{F})$), which also forms the primary mineral constituent of human bones and teeth.

Carbonado

A dark, porous, polycrystalline aggregate of diamond utilized primarily for industrial abrasive applications.

Euxinic Environment

An anoxic and sulfur-rich deep water marine sedimentary environment conducive to the precipitation of sulfide minerals like pyrite in the presence of organic matter.

Borax

A commercial hydrous sodium borate mineral with the chemical formula $\text{Na}_2\text{B}_4\text{O}_5(\text{OH})_4 \cdot 8\text{H}_2\text{O}$, widely used in household cleaning, metallurgy, agriculture, and insecticides.

Feldspar Miscibility Gap

A temperature-dependent phase boundary in alkali and plagioclase feldspar systems where two distinct feldspar phases co-exist rather than forming a single homogeneous solid solution.