I think sandstone is also what causes the pH to be low. My garden area is
mostly sand with clay and needs huge amounts of amendments/organic matter to
grow anything very good. The driveway has areas of pure rinsed sand where the
water runs over it during high creeks. Lots and lots of sand and lots and
lots of clay. There is lime quarries around, but most of my rocks are shale,
sand, and whatever those flat paving stones are made of. There are also lots
of coral fossils lying around, if that means anything.