Hey, thats one from me :-)

Throw in some brown, bang a rough displacement map over the lot, (blending clouds, granite, turbulence and or spots) and you should get pretty-pretty  close. :-)

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!