I recall something about the text being changed in the last update. Let me review that...
Yeah, it's a nonfunctional change. It should currently say
Basalt Monolith doesn't untap during your untap step.
:symtap:: Add to your mana pool.
:3mana:: Untap Basalt Monolith.
If that is its text, then Rings of Brighthearth can be used to generate large amounts of mana by copying the untap ability. With down, you can get two untaps. With these untaps, you can add to your mana pool.
it wouldn't work due to the fact it's a mana ability rings states it cannot copy a mana ability
Basalt Monolith has three abilities, two of which are activated abilities. Of those, only one is a mana ability. The ":3mana:: Untap Basalt Monolith." ability can be copied just fine when it is activated. The ":symtap:: Add to your mana pool." ability can't be copied as it's a mana ability, but the other activated ability can be copied just fine.
Tap the Basalt Monolith to add 3.
Untap the Basalt Monolith by paying 3.
Rings triggers, you pay 2 to copy the Untap ability.
After the copied ability resolves, but before the original untap ability resolves, Tap the basalt monolith to add 3.
Untap ability resolves, and untaps the Basalt Monolith