Mother lode

The term is also used colloquially to refer to the real or imaginary origin of something valuable or in great abundance.

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).

[1] 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,[2] bounded on the east by the Melones Fault Zone.

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.