Tutorio.com

Create the texture : Part 1

1. Create a new layer in a new document in Photoshop.
2. Fill the layer with a medium grey color.
3. Go to Filter >> Noise >> Add Noise. and then use something similar to the following settings.
4. Then go to Filter >> Render >> Lighting effects. Then mess around with the settings until you have this bumpy sort of texture.

Create the texture : Part 2

1. Go to Filter >> Brushstrokes >> Spatter. And then use Spray Radius: 5 and Smoothness:4 for the settings. This will convert the texture from being bumpy to being more of a marbled sort of texture
2. Create a new layer, then Go to Filter >> Render >> Clouds and change the blending mode of the new layer to 'overlay'
3. Go to Filter >> Pixelate >> Pointillize and use the default settings.
4. Go to Image >> Adjustments >> Hue and Saturation. Make sure that you have the colorize box checked off and then adjust the settings till you get a nice rock-like color.

Carvings

At this point the texture is ready for use in 3d programs and other projects creating 'carvings' in your texture is optional

1. Create a new layer and set its blending mode to overlay
2. Select a hard tipped , dark colored brush and draw the carvings.
3. Right click the layer choose Bleding options, select inner shadow and use the following settings.