I like the card concept (generating
based on the number of burrowed creatures) - an interesting idea with a useful niche in earth-based decks.
As OldTrees notes, however, 3
is a lot of quanta to generate per turn per burrowed creature. 1
per turn per burrowed creature might well be more balanced.
Another possibility would be a strip mine (as a spell instead of a permanent) which provides the larger amount of quanta from your original idea (3
per burrowed creature) but only once upon play instead of every turn.
As for the name, diamond seems right for the upped version, but gold seems a bit soft for the unupped version - maybe titanium|diamond as with the earth shield?