Mother lode
Mother lode is a principal vein or zone of gold or silver ore. The term is also used colloquially to refer to the real or imaginary origin of something valuable or in great abundance. Term. The term probably came from a literal translation of the Spanish "veta madre", a term common in old Mexican mining. "Veta madre," for instance, is the name given to an silver vein discovered in 1548 in Guanajuato, New Spain (modern-day Mexico). California Mother Lode. In the United States, "Mother Lode" is most famously the name given to a long alignment of hard -rock gold deposits stretching northwest-southeast in the Sierra Nevada of California, bounded on the east by the Melones Fault Zone. It was discovered in the early 1850s, during the California gold rush. The California Mother Lode is a zone from wide and long, between Georgetown on the north and Mormon Bar on the south. The Mother Lode coincides with the suture line of a terrane, the Smartville Block. The zone contains hundreds of mines and prospects, including some of the best-known historic mines of the gold-rush era. Individual gold deposits within the Mother Lode are gold-bearing  quartz veins up to thick and a few thousand feet long. The California Mother Lode was one of the most productive gold-producing districts in the United States. Now it is known as a destination for tourism and for its vineyards. The California gold rush, as with most gold rushes, started with the discovery of placer gold in sands and gravels of streambeds, where the gold had eroded from the hard-rock vein deposits. Placer miners followed the gold-bearing sands upstream to discover the source in the bedrock. This source was the "mother" of the gold in the river  and so was dubbed the "mother lode".