Near an old fire-trail I found a single fist-size igneous rock that I identified (as an amateur geologist) as belonging to a formation that is not known of in the area but is known to occur in the neighbouring district, although not common there. Naturally I was interested if there was an outcrop and looked for more float samples, but twenty minutes of searching yielded no more samples of the kind. My question is, how reliable are float samples? Is there probably an outcrop? Or assuming my ID was correct, could I just have been that the bulldozer that cut the road all those years ago came directly from the small part of the neighbouring district where these rocks are found. Or did the bulldozer move it from elsewhere on the hill, but there still probably is an outcrop in the immediate vicinity.
Apologies for the rather specific (and long-winded) question, I understand that this Stack Exchange is looking for more general questions, but I would just like to add if it was possible for an intrusive igneous rock such as syenite to be shed from quartz conglomerate? It seems unlikely to me, but that is the main formation above the spot where it was found and could explain its occurrence. (Should I have created a seperate question for this?)