How to Make a DIY Rock Tumbler The Active Family
The process of rock tumbling varies depending on the rock type. Rocks like fluorite, marble, calcite, and obsidian are soft rocks. They shape quickly in a rock tumbler. Marble and Calcite have a Mohs hardness of 3 and will round nicely in three days max. Obsidian and Fluorite have a Mohs hardness of and take up to five days to round nicely.