Quick rocky surface
Quick rocky surface In your document, go to the Channels panel (Window>Channels), and click on the Create New Channel icon. Now, using black and white for your Foreground/ Background colors, perform the exact same steps as in the "Quick Marble" tip: Go to the Filter menu and choose Render>Clouds, then choose Filter>Render>Difference Clouds. Press Command-F (PC: Ctrl-F) a few times to reapply the Difference Clouds filter until you get the desired look.
Click on the RGB channel and fill it with the color you want for your rocky surface. Next, go to the Lighting Effects filter (Filter>Render>Lighting Effects) and in the dialog, set the Light Type to Directional. For the Texture Channel (at the bottom of the dialog), choose the Alpha 1 channel you just created, then drag the Intensity slider all the way to the right to Full .
Finally, try various Properties settings until you have what you're looking for, and click OK. from Bert Monroy