When your Pickaxe Skill get high enough and you're using the best tool available, it only takes a single strike to break up the small boulders strewn about everywhere, not the 'pickable' ones. I can clear an entire Meadow of boulders and get a ton of materials, same near shorelines, the large boulders break up quite easily...and provide a lot of stone. Mining also produces lots as well as the 'petrified bones' once the black rock has been extracted.