Hahaha Thanks! I am an expert with rock tumblers only because I have a lot of them and I have been doing it for several years. I wouldn't consider myself any sort of lapidary pro unless I had all the toys and had mastered them (rock saws, angle grinders, flat lap polishers, cabbing machines/grinding wheels etc etc). My parents offered to buy all the fancy machines for me to advance my rock tumbling hobby to lapidary work, but, my main hobby is breeding ball pythons...everything else is just a secondary interest.
Yeah, you don't see goofs because the great thing about rock tumbling is that you can just toss them back in the barrel and aside from internal fracturing: any mistakes can be corrected at the cost of losing mass on the stone...
One of my costliest goofs was using a beautiful 468g. Red-Blue Corundum (Ruby/Sapphire) I imported from a mine in China. I put in a tumbling barrel with petrified wood chips: My thought was that since the Corundum was harder than the petrified wood-and the same hardness as my silicon carbide grit-that it should wear down very slowly. This would have been true, but, the higher hardness stones don't scratch-they splinter and chip. At the end of two weeks of tumbling I had a 20g sphere of ugly grey-blue sapphire and everything else in the barrel was liquified by the corundum dust...they say not to tumble Rubies and Sapphires-'they' are right...
Photo #344
Lesser (+Het Gravel or YB), and a piece of pink chalcedony from the West Coast, USA.