Rock Pikmin are a newly discovered type of pikmin in the upcoming game Pikmin 3for the Wii U. Not much in known about them at this point. But in the Official Trailer shown at E3 2012, their hard bodies can break crystal walls, ice surfaces, and enemies when thrown at them. Their tradeoff is they walk a bit slower like Purple Pikmin, and they can't latch on to enemies, instead they keep raming into the enemy. Unfortunately even with size, their lift weight is one pikmin like all other types except Purple.
They have Purple Flowers unlike the other original 5 types of pikmin. Rock Pikmin along with bulbmin, mushroom pikmin, and pikmar are the only types of pikmin that aren't based on color.