When using a tumbler to polish rocks, it is important to check the hardness of the stone, and/or KNOW what stone it is. The reason is that if you tumble softer stones with harder stones, the harder stones will grind the soft ones into sand.
About a week ago, my Bestie found this cool rock. (The big one).
It was still dirty and I thought she had found a Petoskey Stone, which is fossilized coral. She said she found it up by Lead, SD. Petoskeys are found in Michigan, especially near the Great Lakes. They are not found in the Black Hills of SD.
After washing it off, I saw no coral formations, so it is not a Petoskey. It looks like Dolomite with these cool quartz veins. It should look awesome once it has been polished.
I ran it in Stage 1 (46/70 abrasive grit) for a week. Took it out today and ... oh my.
What I thought was quartz, which has a hardness of 7 on the Mohs scale (diamond is 10), turns out to be Calcite, which has a hardness of 3.
It still turned out to be a cool rock. I cleaned out the holes with a waterpik and they are connected. There might be a pocket of crystals in the back. I put it under the stereoscope and can confirm they are Calcite crystals. Calcite is very common in limestone and dolomite. Quartz, not so much.
Bestie is happy with her cool find now that it is all clean and smooth. I got a reminder to check the rocks carefully before starting them in the next cycle. Back to the basics.
