Many gerbils enjoy a dust bath. That is dust bath... using Chinchilla sand or dust in a small container big enough for the gerbil to roll around in. You can buy the sand or dust at the pet store. I would not recommend dust or sand found out in the backyard or at the beach. Then chinchilla sand or dust is very small grind.
Christmas Bonnet with Silver Bow for Guinea Pig, Chinchilla or Rabbit