I have a customer who is wanting red lava rock put into his beds instead of mulch, Now the local guy that carries it around here sells it in bulk, by the ton. This job i'm working on would normally be about 12 yards of mulch. Does anyone know how to convert this to yards to be able to tell me how many TONS of lava rock to buy? Any help would be great! I've never put down the lava rock or any type of rock in beds before, I've only done mulch! Please let me know ASAP!