Easier to work than clays, better consolidated than sands, loamy soils are an excellent growing medium. Dig into your soil when it's dry. A sandy soil will seldom exhibit clods. Any clods that do form will crumble easily. A loamy soil will have clods that can be sliced cleanly with a shovel.
Clay soils tend to form hard, persistent clods.
Rather than slicing through them, a shovel will get stuck or will shatter the clod into many hard, little blocks of soil. If you're in doubt, take a soil sample to your local county extension agent or soils lab. If you have a sand or clay soil and wish to improve it, add large quantities of organic matter. Compost and dead leaves are excellent. Do not use sawdust or wood chips.