The stuff you put into your tumbler especially to polish the rocks in the final stage is frequently made of cerium oxide, tin oxide, chrome oxide, or aluminum oxide. It's really a method of grit historically generally known as a polishing compound and is amazingly great. As an example, this https://www.facebook.com/permalink.php?story_fbid=pfbid0tgzbP3xvRNr7vz9ugJqxZ6qpW5rJYkaQNiedGwxis84bSqzVZmu65mEhkn4EEZaRl&id=61562415773754&__cft__[0]=AZUrPa6046vl1x5Ftd0n16emkDMeojSzj35m7-jdmqDLTpbX-jZAVM_uwJUldY-XHZ04cAZ6vkYT8gm1B3edr4TeP-Apugz1_-4oH5k3it3N097r57Ozvke5N3NZ60v_2AyVWmIqx2dFIvr0wOUjIISc44eGuRP-V0ExBtxAs2yhT7Ru9DNLZcRk2HWmDM0LShzlX5f-MGd7fLEthGwT_Rxd&__tn__=%2CO%2CP-R