Hickory Creek Boulders Central Valley California quarry producing a wide range of materials from the rubble to large boulders. Materials are shipped bulked 18 to 24 tons throughout California. Smaller orders shipped on pallets anywhere requested. Harvest Season Boulders are a very hard quartz rock material that is a beautiful mixture of fall brown and gold colors. Rock material is available in 12 inches through 60-inch sizes, most commonly 24 to 36 inches.