Fill it with black.
Duplicate your base. Now with the second layer, go ADJUST - ADD/REMOVE NOISE - ADD NOISE.
Match your settings to mine below:
So far your icon texture should look like this:
Create a New Raster Layer. Select any random brush and size it 1px. While white, draw several "scratch" marks. You may have to go over a section a few times to get your mark to show up.
Merge all layers and duplicate your base. Set it to Multiply 15%.
You're finished!
To use your texture, paste it as a new layer on top of your icon and set it to Screen 100%.
If the texture isn't dark enough, you can always duplicate it.
