This rock yard should be a field trip for college geology students. There's a wealth of natural products, all clearly marked and organized, for all of your backyard needs (except maybe grass): limestone, flagstone, gravel, soil, mulch, boulders. They will mentor the do-it-­yourselfer, give guidelines on figuring out how much material you'll need and offer advice on how to lay your flagstone, whether you want to mortar it or fill it in with several of the beauteous types of crushed granite there. They'll even refer you to landscape companies to hire. If you see a chunk of quartz for a garden accent or a "holey rock" that resembles a steer skull — great for planting small cactus in — load them up in one of their big rice sacks, and they'll charge by the pound. Tip: Avoid Saturday mornings, when all the DIYers are out.