google_color_url="FFFFFF"; Near the Sierra Madre Mountains, in the Hot Park Area, barite is commonly found, a couple of miles southwest of Encampment. Rainbow agates are plentiful in the Wind River near Riverton, Fremont County. The True Worth of Agates. Is the watermelon rock you mentioned in article of the tourmaline family? Rockhounding in eastern Wyoming offers a lot of opportunities to find a wide variety of rocks and minerals.