Red rouge powder can be used as a final polish when tumbling rocks. We have used it to get a glass like finish on apache tears/obsidian and agates as well as other stones. Red rouge is basically ferric oxide (iron oxide) or rust in the form of a very fine powder. As I said, red rouge works great as a final polish. Another benefit of using red rouge is it is relatively cheap compared with other polishing powders such as submicron aluminas (Raybrite TL), tin oxide, or cerium oxide. The place I buy grits and polishes from, sells red rouge powder for $7.10 a pound. That is cheap compared to cerium oxide at $34.50/lb, and tin oxide at $49.99/lb. And it is very cheap compared to the submicron alumina polish at $8.20/oz.
But there are issues with using red rouge too. It is messy. It will stain stuff red. With many rocks, this is not a big issue. The red rouge will stain the rocks red along various cracks in the rock. But if you now soak the rocks in water mixed with Iron Out, the Iron Out will remove the rust stains. But you need to be careful with the rocks you put into the Iron Out. Iron Out will also dissolve calcium, which makes up some rocks you might want to polish such as Labradorite (Calcium sodium aluminum silicate). We learned this the hard way as a nice piece of labradorite came out of the Iron Out looking kind of ugly. The red rouge will also stain your tumbler barrels, or bowls red. Again, this not a really big deal.
So red rouge powder is a cheaper way to get a glass like finish on many rocks as long as you are willing to deal with the mess.
