The Stuff you put in to the tumbler exclusively to polish the rocks in the final phase is usually made of cerium oxide, tin oxide, chrome oxide, or aluminum oxide. It's a type of grit historically known as a polishing compound and is amazingly fine. The primer acts as a https://www.quora.com/profile/Trevor-Flatcher-2/Understanding-the-Chemical-Stability-of-Silicon-Carbide-Special-Ceramics-https-www-macrocosmmaterial-com-news-Underst