107.4h

The snow mana symbol {S} represents one generic mana in a cost. This generic mana can be paid with one mana of any type produced by a snow permanent (see rule 205.4g).

Boreal Druid. A mana produced by any snow creature  which equipped Paradise Mantle also can be spent this way.

Effects that reduce the amount of generic mana you pay don't affect {S} costs. (There is no such thing as "snow mana"; "snow" is not a type of mana.)

Heartstone doesn't reduce Frost Raptor's activated ability's activation cost to S.