Many rocks can yield pigments, some make you work harder for them than others. Sedimentary rocks like Limestone and Shale are ideal for pigment making as they break and can be ground down easily as they have higher clay content. Slate, a Metamorphic rock is similar in this regard. Below is an identification chart to help you identify rock types. Additional information is also shared below the chart for gathering earth colors, including links for rock identification, tips and tricks and other wonderful earth science knowledge.
Our Rock identification Chart can also be downloaded HERE as a PDF !
Testing Rocks In The Field For Color
An easy and effective way of testing rocks for pigment production in the filed is with the following test. Take your found material (rock) first use your sense of touch to try and determine it’s hardness and texture. Most rocks that lend to beautiful pigments tend to feel lighter, and less dense, and softer. If you feel the rock you’ve selected has the potential to yield color taking those sensory observations into mind, the next step is to wet or submerge your rock in water until the surface is coated and wet. Find another rock, preferably larger and again, using touch to guide you – one that feels harder and denser than your sample. Take the wet sample you collected and rub it against the other rock. Use your sense of touch, sight and sound to observe what is happening as you test your sample. Is your color sample leaving a colorful residue behind, is there a gritting sound against the rock (you will notice a discernible difference between hard rocks and softer pigment bearing rocks). If your sample yields color easily – this is a good rock to take home to your studio to process. Some rocks like sandstone that are colorful my not always leave color behind with this test, and can still be washed, ground and levigated to yield pigment as well. Use your knowledge, judgement and what calls to you and don’t be afraid to experiment!