So here's the bottom line: If you can process your colored rocks or soil into tiny, consistently sized particles, you can make paint from them. Pastels or drawing sticks too (but that is the subject of another post).
Some of the above pigments come from soil, some (like the magnetite on the far right) started as sand, and some are from rocks I found that were soft enough for me to grind into a powder. One way to know if a rock will be soft enough for you to crush (I used a hammer and an anvil, and then a mortar and pestle) is to rub it across concrete, or another hard rock surface. If your rock leaves a colored mark, you will be able to use it.
Not every paint I make ends up the same color as the rock or soil it came from, sometimes the pinks and dark reds turn orange and brown, and often the blues and greens mull into blue-grays and khaki shades of green.
Some samples I gather make a "stronger" paint that others. I'm finding my foraged yellow and red ochre pigments make paints with the highest tinting strength.
Below is a video that demonstrates how I use water to process the colored soil I find. This process (called levigation) produces a powder I can use to make paint and pastels:
A few other ways to get usable pigment from your soil and rocks:
If you are interested in the process of making handmade watercolors, visit my previous blog post.
Happy mulling!
Happy mulling!