Lori, you might try a leaf blower, or if you don't have access to one maybe take a shovel and scoop everything up and spread out on the driveway then seperate using a broom then replace the lava rock with the shovel. Good luck.

Another trick might be to use a propane like torch or pour kerosene over the stones. Lava is quite resistant to heat and pine needles arn't.

Put a fresh new batch on top. just a very thin layer, it doesn't have to cover 100%, but it will save you 1/2 a summers work, unless your retired?!