Stones are fun to tangle. It really gives you a very tactile experience. First you need to choose the right stone. As I walked along the beach I saw many to choose from. If the shape looked promising I picked it up. I turned it over, I felt it to see if it was smooth enough. If it felt right I put it in my pocket. Sometimes I would catch myself playing with the rock in my pocket later that day - feeling the shape in my hand.
Washing the stone would reveal other aspects to the stone. I would discover cracks, and/or see that the water would darken the color of the stone.
After it dried I would turn the stone in all directions, trying to see if there were any tangles that seemed to be wanting to be drawn on that particular stone. When I 'discovered' them it was almost a Eureka moment!
I did most of my tangles with the Sakura IDentipen and the white graphite pencil. On the really dark rocks I used my white gelly roll pens.
I have accumulated quite a few rocks now. These rocks are a combination of rocks I found along the shoreline in Rhode Island and rocks that I have purchased. I discovered that my big box home improvement store sells bags of rocks for landscaping. The river rock bags had several lovely shapes! (If you live in a Northern climate you may need to wait for spring to see these in stock again.)