Gold Mining In Indonesia

Gold is found in ores made up of rock with very small or microscopic particles of gold. This gold ore is often found together with quartz or sulfide minerals such as Fool's Gold, which is a pyrite. These are called lode deposits. Native gold is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits (called placer deposits). Such free gold is always richer at the surface of gold-bearing veins owing to the oxidation of accompanying minerals followed by weathering, and washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets.
Gold sometimes occurs combined with tellurium as the minerals calaverite, krennerite, nagyagite, petzite and sylvanite, and as the rare bismuthide maldonite (Au2Bi) and antimonide aurostibite (AuSb2). Gold also occurs in rare alloys with copper, lead, and mercury: the minerals auricupride (Cu3Au), novodneprite (AuPb3) and weishanite ((Au, Ag)3Hg2).
Recent research suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.
The world's oceans contain gold. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 fmol/L or 10-30 parts per quadrillion. In general, Au concentrations for Atlantic and Pacific samples are the same (~50 fmol/L) but less certain. Mediterranean deep waters contain higher concentrations of Au (100–150 fmol/L) attributed to wind-blown dust and/or rivers. At 10 parts per quadrillion the Earth's oceans would hold 15,000 tons of gold. These figures are three orders of magnitude less than reported in the literature prior to 1988, indicating contamination problems with the earlier data.