NEW MEXICO RIVER ROCK 2"-4" New Mexico River Rock-Perfect for decorative or practical use, river rock gravel is the preferred choice for many landscape projects. River rock gravel is made of rounded stones that are polished to remove sharp edges. Gathered from the rock bed of streams and creeks, river rock gravel is completely natural. These rounded rocks are a great option for garden or lawn edges, as they can be walked on comfortably and hold ground level gravel in place.