Caliche for ranch roads on clay
Caliche is a calcium-carbonate gravel that compacts hard and holds well over clay soil. It's the standard for long ranch driveways across Van Zandt, Rains, and Wood counties because it bonds when wet and stays put through East Texas weather.
Downside: it's dusty in dry weather and it doesn't look as polished as crushed limestone. Most ranch customers don't care; suburban customers sometimes do.
Crushed limestone for higher-traffic and aesthetic
Crushed limestone — usually a 3/4 inch or 1.5 inch — is heavier-traffic material. It works well over either clay or sandy soil with a proper base. It looks cleaner than caliche and it holds up to delivery trucks, heavy equipment, and frequent traffic.
We use limestone on most commercial driveways and on residential driveways where the customer wants a finished look. Cost is higher per ton.
Road base for the foundation under the surface
Road base is a graded aggregate that goes under whatever surface rock you choose. On a long driveway over soft clay, you need 4-6 inches of road base compacted before the surface rock goes down. Skip this step and the driveway ruts out the first season.
Most failed driveways we get called to fix didn't have a base. They just dumped surface rock on dirt and called it done.
River rock and pea gravel: not driveways
River rock and pea gravel look great in landscaping but they're round, which means they roll. Vehicles displace them. They migrate to the edges. Don't use them as a driving surface on anything longer than a walkway.
Bottom Line
Pick the rock for the application, the soil, and the traffic — not for the price-per-ton. The cheapest material on the wrong driveway costs more in maintenance over five years than the right material at install.