Stone, rock or gravel roads, driveways and paths need materials with coarse, sharp, jagged corners to lock together. Smooth, rounded stone moves and does not create a solid surface.
Building a gravel, stone or rock surface can require 3 layers – solid base foundation #3 stone (clean stone), middle layer for good drainage (#57 stone), and a top layer for appearance and support (#411).
The top layer should be rough, angular stones as these will give a firm, stable surface. This final layer consists of smaller gravel mixed with coarse rock dust, called fines. Blending small stones and rock dust lets the rock fit tightly together to form a stable, solid surface that can support vehicles.
And to help drainage further, form the stones so there is a slight peak in the middle and down to the sides. By crowning the driveway, you will move rainwater off the surface.
Pea gravel, shore gravel and river rock look nice, but the rounded, smooth surface doesn’t lock together like angular fragments of crushed stone. These stones will shift under a weight load.