Native Gold
Chemical formula: Au
Native gold is a naturally occurring elemental noble metal, valued for its color, corrosion resistance, and malleability.
Description
## Characteristics Native gold typically occurs as irregular nuggets, flakes, wires, or dendrites, and less commonly as well-formed crystals. Gold crystals are usually small, with octahedral, dodecahedral, or cubic habits. It often forms irregular aggregates, known as nuggets. The color of gold is intensely yellow, becoming lighter, almost whitish-yellow, with increasing silver content. In very thin flakes, gold can exhibit a blue or green color in transmitted light. ## Physical Properties Gold is a very soft metal, with a Mohs hardness of 2.5-3. It is characterized by a strong metallic luster. It is opaque. The density of gold is very high, approximately 15 g/cm³, which is one of its characteristic features. Gold does not exhibit cleavage, and its fracture is hackly. ## Colors and Varieties The typical color of gold is an intense, rich yellow. Color varieties depend mainly on impurities of other metals, especially silver. Gold with a high silver content is called electrum and has a lighter, silvery-yellow color. ## History and Name Gold has been known to humanity for thousands of years and was one of the first metals used by humans. Its name comes from the Old Slavic word "zolto". It was valued in many cultures as a symbol of wealth, power, and divinity. In antiquity, it was used to make jewelry, ornaments, and coins. Due to its corrosion resistance and rarity, it has served as currency and a standard of value for centuries. ## Applications Gold is widely used in jewelry making. Due to its excellent electrical conductivity and corrosion resistance, it is used in electronics, especially in the production of high-quality connectors and components. It is also used in dentistry, medicine, and as an investment and financial reserve.
Diagnostic features
## Identification Native gold can be identified by its characteristic, intensely yellow color, strong metallic luster, and high density. It is very soft and malleable, and can be scratched with a copper wire or knife. Its streak is shiny yellow. It often occurs as irregular flakes, wires, or nuggets. ## Distinguishing from Similar Minerals Gold is sometimes confused with pyrite ("fool's gold") or chalcopyrite. Pyrite has a brighter, brassy-yellow color, is much harder (6-6.5 on the Mohs scale), brittle, and has a black streak. Chalcopyrite has a more greenish-yellow hue, is also harder and brittle. Gold differs from them in its malleability, softness, and shiny yellow streak. ## Crystal Forms Gold crystals are rare, but if they occur, they usually have an octahedral, rhombic dodecahedral, or cubic habit. More often, it is found as irregular nuggets, flakes, wires, fibers, dendrites, or granular aggregates, forming nuggets.
Geological environment
## Genesis Native gold forms in hydrothermal processes associated with volcanic activity and magmatic intrusions. Hot gold-rich solutions circulate in rock fractures, where, due to changes in pressure and temperature, gold precipitates and crystallizes. It also occurs in secondary, so-called placer (alluvial) deposits, where it is concentrated in river and glacial sediments as a result of the erosion of primary deposits. ## Mineral Associations Native gold often co-occurs with quartz, pyrite, chalcopyrite, arsenopyrite, galena, sphalerite, as well as other ore minerals and sulfides. In placer deposits, it is accompanied by heavy minerals such as magnetite, ilmenite, and garnets. ## Localities Significant deposits of native gold occur worldwide. Important historical and contemporary localities include: Witwatersrand in South Africa, Kalgoorlie in Australia, the Klondike region in Canada, Sierra Nevada in California (USA), the Urals in Russia, and numerous places in Brazil and China.
Rarity
Very Common
Collector aspects
## Quality Criteria The most prized specimens of native gold are well-formed crystals, especially those with distinct faces and forms. Large nuggets of interesting shapes, free from impurities and damage, are also highly sought after. Specimens with visible inclusions of quartz or other minerals can be attractive due to their aesthetics and geological context. An intense, pure yellow color is also an important criterion. ## Popular Localities The most prized gold specimens come from historical and contemporary mining regions such as California (USA), Australia (e.g., Victoria, Kalgoorlie), Colombia, Brazil, Russia (Urals), and Canada (Klondike).
Care and storage
## Cleaning Native gold can be cleaned gently using a soft brush and warm water with a small amount of mild soap. After washing, rinse the specimen thoroughly with clean water and dry with a soft cloth to avoid deposits. ## What to Avoid Avoid using aggressive chemicals, such as strong acids or bases, which can damage the surface of the gold or contaminate other minerals with which gold may co-exist. Gold is soft, so it should be protected from scratches and impacts. It is not sensitive to sunlight or typical temperature changes, but extreme conditions can affect accompanying minerals. ## Storage Gold specimens are best stored in individual, soft pouches or in padded boxes to prevent scratches. Due to its value, it is recommended to store it in a safe place, away from moisture, which could promote corrosion of other metals in the case of alloys.