granite pattern uses a simple 1/f fractal noise function
to give a good granite pattern. This pattern is used with creative color maps
stones.inc to create some gorgeous layered stone
As a normal pattern it creates an extremely bumpy surface that looks like a gravel driveway or rough stone.
Note: The appearance of the granite pattern depends on the noise generator used.
The default type is 2. This may be changed using the
noise_generator keyword. See the Pattern Modifiers section: noise_generator.