<P> 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 . </P> <P> 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 11 - kilometre - long (6.8 mi) silver vein discovered in 1548 in Guanajuato, New Spain (modern - day Mexico). </P> <P> 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 . It was discovered in the early 1850s, during the California gold rush . The California Mother Lode is a zone from 1.5 to 6 kilometres (0.93 to 3.73 mi) wide and 190 kilometres (120 mi) long, between Georgetown on the north and Mormon Bar on the south . </P> <P> 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 15 metres (49 ft) 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 . </P>

Where is the mother lode located in california