This is a really great and interesting video on how International Bonsai Master Mashiko Kimura prepares a volcanic type rock for a rock planting. The closest rock in the USA would maybe be a piece of Lace Rock. It looks like he is using a reciprocating saw with unknown blade type and some type of weasel and makita or fordem power tool. I have posted the video under Kimura’s educational video page, shown under Educational Videos listed under Bonsai Basics.