I’m not a mineral person going to be honest (I work in healthcare lol), so not sure I can really answer your questions. Also sorry being a bit cagey didn’t want to dox myself before a google, like felt 99% sure this was a common mineral, but again not a mineral person.

Basically I lived in some foothills along a ravine made of granite. Home 1 I think we had a neighborhood well and home 2 was a personal well. I can’t list the equipment being used to soften the water (if at all), I just know neither were on town water and home 2 I helped my dad install a softener since there wasn’t one (which tbh didn’t help too much besides making the water coming out of the faucet less cloudy and mildly less thirst inducing).

I don’t think my hometown has a lot of limestone (idk may be wrong, like said I’m not a mineral person, all I know it’s a granite ravine) so can’t comment too much beyond that. This was just my experience with water growing up and what put me off it for a long time.