Sandstone

1. Start with a light color and slowly add darker shades.

2. Create the lines of the sandstone. The curviture of the lines will determine the form of the rock.

3. Build upon the lines with warm tones.

4. Create warm highlights with yellow. Make shadows using yellow's complimentary color, purple. Add in some white highlights.

Pro Tip:  A white gel pen or acrylic marker works great for creating highlights at the end!