Quartz reef mining is a type of gold mining in "reefs" (veins) of quartz. Quartz is one of the most common minerals in the Earth's crust, and most quartz veins do not carry gold, but those that have gold are avidly hunted by prospectors. In the shallow, oxidized zones of quartz reef deposits, the gold occurs in its metallic state, and is easily recovered with simple equipment. Quartz reef mining played an important role in 19th century gold-mining districts such as Bendigo, Victoria in Australia, Central Otago in New Zealand, and the California mother lode. Source: Wikipedia (en)