Never been much of a rock hounder myself so I don't have any personal spots to recommend. However the first place I would stop is Ottingers rock shop at the north end of town. Not only do they sell a little of everything from fossils to gieger counters, most of the employees I have met are big time rock hounds themselves. If you get the chance to meet Lin himself, you'll have found the mecca for all things rock in the SE portion of Utah.