lode

n. [ AS. lād way, journey, fr. līðan to go. See Lead to guide, and cf. Load a burden. ] 1. A water course or way; a reach of water. [ 1913 Webster ]

Down that long, dark lode . . . he and his brother skated home in triumph. C. Kingsley. [ 1913 Webster ]

2. (Mining) A body of ore visibly separated from adjacent rock. [ PJC ]

3. Especially: (Mining) Any regular vein or course of valuable mineral, whether metallic or not. [ 1913 Webster ]

4. Hence: A concentrated supply or source of something valuable. [ PJC ]

mother lode a large concentrated source of mineral or other valuable thing, from which lesser sources have been derived; -- often used figuratively. The term may have been originally applied to real or imagined large deposits of gold from which smaller granules were washed downstream, there constituting a diluted source of gold, and hinting at the richer source from which they were derived; as, to hit the mother lode. [ PJC ]