I know some good driftwood places, and locations for granite and such, even a couple of interesting gemstone localities, but I don't think you'll find much that's similar to ryuoh stone locally. CT geology doesn't match up much with that of Japan/Asia-in-general where the fancy amano-style scaping rocks come from. Most of Japan was formed by volcanic activity... CT is mostly made of glacial deposits. Different kinds of rock and all.
But, you never know. Maybe look into local shale quarries... shale at least has the kind of layering that, with a little sandpaper "weathering" might get you a similar effect.