Minerals – Key Vocabulary

20 English vocabulary flashcards covering fundamental mineralogy terms and examples discussed in the lecture notes.

Mineral

A naturally occurring, inorganic solid with a definite chemical composition and an ordered crystalline structure.

Rock-forming minerals

≈100 common minerals that combine to make up the vast majority of Earth’s crustal rocks.

Agate

Banded, cryptocrystalline variety of silica that forms in volcanic cavities; prized for its fine layers and colors.

Quartz

Silicon dioxide (SiO₂); one of Earth’s most abundant minerals, often forming hexagonal prisms and making up most clean sand.

Mohs Hardness Scale

Qualitative 1–10 scale created by Friedrich Mohs (1812) ranking minerals by their ability to scratch softer substances.

Streak

The color of a mineral’s powdered form, observed by rubbing it on unglazed porcelain; more reliable than surface color.

Cleavage

A mineral’s tendency to split along flat, parallel planes where atomic bonds are weakest.

Fracture

Irregular or uneven breakage of a mineral when it does not cleave along planes of weakness.

Luster

The way light reflects from a mineral’s surface, described as metallic, vitreous, pearly, silky, etc.

Specific Gravity

The ratio of a mineral’s density to that of water; indicates how heavy the mineral feels for its size.

Crystal Habit (Form)

Characteristic external shape a crystal tends to develop, such as prismatic, tabular, acicular, or equant.

Hardness

Resistance of a mineral to scratching; tested by the scratch test and expressed using the Mohs scale.

Silicates

Largest mineral class built from silicon-oxygen tetrahedra; accounts for >90 % of rock-forming minerals.

Carbonate minerals

Minerals containing the (CO₃)²⁻ anion; effervesce with dilute HCl (e.g., calcite, dolomite).

Halides

Minerals composed of halogen anions (Cl⁻, F⁻, Br⁻, I⁻) bonded to metals; example: halite (NaCl).

Oxides

Minerals in which oxygen is bonded to metal cations; includes important ores like hematite (Fe₂O₃).

Sulfides

Minerals consisting of metal cations combined with sulfur; common ore minerals such as galena (PbS) and pyrite (FeS₂).

Sulfates

Mineral class containing the sulfate anion (SO₄)²⁻, e.g., gypsum (CaSO₄·2H₂O).

Piezoelectric effect

Ability of certain crystals (e.g., quartz, topaz) to generate an electric charge when subjected to mechanical stress.

Fluorescence (in minerals)

Emission of visible light by certain minerals when exposed to ultraviolet radiation, causing them to glow brightly.