Gold is commonly viewed only as a metal used in currency or jewelry, leading to confusion about its scientific classification. However, from a scientific standpoint, gold found in nature is definitively classified as a mineral. The distinction between a “metal” and a “mineral” is based on specific criteria used by geologists and mineralogists. This classification holds true for naturally occurring gold, which is formally known as native gold.
The Scientific Criteria for a Mineral
The scientific community applies five specific requirements to classify any substance as a true mineral. First, the substance must be naturally occurring, meaning it formed through natural geological processes rather than being synthesized in a laboratory. A mineral must also be a solid substance under normal surface conditions, which immediately excludes liquids or gases.
Third, a mineral must be inorganic, meaning it cannot be a compound or product derived from life processes. It must also possess a definite chemical composition, expressed by a precise chemical formula, though some variation is allowed. Finally, a mineral must exhibit an ordered atomic arrangement, often referred to as a crystalline structure. This internal, repeating pattern of atoms distinguishes minerals from amorphous solids.
Applying the Criteria to Native Gold
Native gold, which is gold found in its elemental state, satisfies all five scientific criteria for mineral classification. The metal is naturally occurring, found in hydrothermal veins and alluvial deposits formed by geological activity within the Earth’s crust. It exists as a solid under all standard Earth temperatures and pressures, meeting the physical state requirement.
Gold is considered inorganic because its formation is a result of geothermal and magmatic processes, not biological ones. Its chemical composition is definite and simple: the chemical symbol Au, representing nearly 100% purity in its native state. The final criterion is met by gold’s internal structure, where its atoms are arranged in a highly symmetrical face-centered cubic lattice. This repeating atomic framework confirms gold’s identity as a crystalline solid and a mineral.
Gold’s Classification as a Native Element
Gold belongs to the Native Elements class of minerals, which includes pure substances like silver, copper, and carbon (diamond and graphite). This classification means the mineral is composed of a single element, rather than being a chemical compound of two or more elements like quartz or pyrite. The simplicity of its composition contributes directly to gold’s distinctive physical properties.
Its face-centered cubic structure gives gold its malleability and ductility, allowing it to be hammered into thin sheets or drawn into fine wires. Gold exhibits a high specific gravity, measuring 19.3 grams per cubic centimeter when pure, which explains why prospectors easily separate it from lighter materials through panning. Being a Native Element, gold is chemically inert, resisting reaction with oxygen and most acids. This inertness allows it to maintain its bright yellow luster and prevents it from rusting or tarnishing.