lode vs mother lode

lode and mother lode both are nouns.

Word	Noun	Adjective	Verb	Adverb
lode	Yes	No	No	No
mother lode	Yes	No	No	No

As nouns, mother lode is a hyponym of lode; that is, mother lode is a word with a more specific, narrower meaning than lode:

lode: a deposit of valuable ore occurring within definite boundaries separating it from surrounding rocks
mother lode: the main vein of ore in a deposit

Other hyponyms of lode include champion lode.

lode (noun)	mother lode (noun)
a deposit of valuable ore occurring within definite boundaries separating it from surrounding rocks	the main vein of ore in a deposit