To discover the unworldly geologic novelties of the Gem State, all that is required is a good map, a sense of adventure, and Idaho Rocks , a guide to 60 of the most compelling geologic sites in Idaho. The well-chosen destinations span the state's geologic history from the 2.6-billion-year-old gneiss in the Panhandle to 2,000-year-old lava at Craters of the Moon, and from gold and silver deposits hidden in Idaho's mountains to visible scars from recent...