Ground Walnut Shell is used in the finishing stage of polishing metals and as a cushioning agent in the tumbling process, particularly for fragile materials (e.g., opal, tanzanite and turquoise) or those with a Mohs hardness of 4-1/2 and below (e.g., shell, coral, ivory, amber, seeds, and nuts). When tumbling soft, irregularly-shaped, or large materials, you'll need a higher volume of media, typically 50-60% of the load.
When polishing metals, the media size should be small enough to pass through any openings in the pieces you're finishing, or large enough to avoid sticking in any openings. For polishing sterling silver items and brass shell cartridges, a small amount of Red Rouge powder is often added to the ground walnut shell. Each piece of Fine-Ground Walnut Shell in the 1 Lb. package averages about 1/16" x 1/16" x 1/16".