02-01-2011, 06:30 AM
The "layers" are most often seen in sedimentary rocks, and the ceiling tiles are a good representation of this formation. I have not heard of the foil method. I have also simply "scarred" partly dry spackling compound with an old xacto blade to form sedimentary rocks.
Igneous rocks (like granite) are more uniform and have no discernible layers. You can simulate those by carving, or by using crumpled foil as a mould. Sometimes outcroppings will be smooth where worn by glaciers (if you're in such an area) or jagged if broken (e.g. by blasting a cut for the right-of-way). Most commercial rock moulds are of this type.
Hope that helps.
Andrew
Igneous rocks (like granite) are more uniform and have no discernible layers. You can simulate those by carving, or by using crumpled foil as a mould. Sometimes outcroppings will be smooth where worn by glaciers (if you're in such an area) or jagged if broken (e.g. by blasting a cut for the right-of-way). Most commercial rock moulds are of this type.
Hope that helps.
Andrew