Gold as a mineral

Gold is a native element mineral. It is also a rare mineral. The name is derived from a Sanskritic word denoting that metal. Gold features jagged fracture which in mineralogy means the ability of the mineral to break along uneven, random surfaces not related to internal structure of the crystal. Gold shows no cleavage i.e. the ability to crack and break upon impact or under pressure along specific directions called cleavage planes. Sheen of gold is strong and metallic. It rarely forms cubic, rhombicuboctahedron- or rhombic dodecahedron-shaped crystals. It usually shows lamellar, bladed, filiform or acicular habit. Occurs in compact, fibrous, plumose or bladed aggregates. Forms dendrites, wires and fine powder (so-called flour gold). Sometimes it forms lumps or fair-sized nuggets. It is isostructural with silver and native copper. It is further malleable, flexible, shapeable, opaque, ductile (a 160 m long wire can be produced out of 1 g of Au). It is also good conductor of heat and electricity. It often contains isostructural impurities of silver (electrum), mercury (goldamalgam), copper (auricupride), palladium (skaergaardite), rhodium (rhodite), yttrium (iraurite), platinum (platinum gold), bismuth (maldonite).

Application:

• Commonly used in jeweller’s craft for manufacturing of gold jewellery.
• For manufacturing of ornamental, church and utilitarian objects (the largest product made of pure gold is the sarcophagus of Tutankhamun weighing 110 kg).
• It is also one of the most sought-after and valued collector’s stones (the largest nugget was found in Chile in 1951 – 153 kg; gold nuggets weighing 68 kg, 71 kg, 85 kg and 92 kg were found in Australia).
• It provides basis for monetary systems and is used in coinage.
• Utilized in electronics (to produce joints).
• For gilding other metals.
• To produce special glass type.
• A component of precious alloys.
• Used in medicine and dentistry.
• Gold compounds are used as a therapeutic agent in rheumatoid arthritis (administered intramuscularly). They inhibit lymphocyte proliferation, release of lysosomal enzymes, production of reactive oxygen forms in macrophages and production of interleukin 1. Side effects may include photosensitive rash, upset stomach and kidney damage. Isotope 198Au (half-life period: 2.7 days) is used in therapy of some tumours and other diseases.

Occurrence in the world:

• Republic of South Africa – area of Johannesburg (estimated reserves: around 70,000 t)
• Russia – Aldan, Kolyma, Ural
• Australia – Kalgoorie
• People’s Republic of China
• United States
• Canada