Golden Sierra River Rock Boulders These boulders are quarried out gravel beds along the rivers of central Sierra Nevada mountains. The surfaces on these boulders have been smoothed by thousands of years of river wash with sand and gravel wearing down the rough surfaces. Bulk quarry direct shipments range in size from about 500 pounds to about 4,000 pounds and will have light amounts of river sediment or sand on them. Individual specimens and sized boulders that have been cleaned are available. Larger specimens can be chosen from field photos and can be specially ordered. Bulk shipments on these boulders range from gold, tan, red, and brown color tones.