Here is a method for creating realistic stratified rock.
An article from one of our model railroad friends suggested using ceiling tiles to make stratfied rock. When I mentioned this to John Lavender, a club member, he suggested using insulation board, some of which was lying about the club room. Apparently, this type of foam insulation board is quite common in the building trade.
Three layers of this board were used to create an eight foot long cutting on Ilkeston Woodside MRC's layout kimberley Station and it only took an afternoon to carve. Best results are acheived with haphazard horizontal cuts with a scalpel, adding more accuratley placed vertical cuts to finish. The illustration below shows two small test pieces which were used on both Snitzl and Kimberley.