After trying out 10 to 20 of each type of rock, I concluded that they eventually all drop an average of between 6 to 10 Red Bricks every 20 chops, and so I just stuck to breakdown Rock Outcroppings. Maybe luck was with me, but I did manage to get a Gold Nugget once every 6 - 8 Rock Outcroppings I cleared.
As for the Cottages, I only have 16 of them, so I have them all out to maximize my chances of encountering the Cyclonicians and also make the best of their long recycle time. I find it more "profitable" to wait 4 hours for 16 Cottages to recover than 4 hours for a handful of 3 to 4 Cottages.