In this helpful guide to the Gem State and the western half of the Big Sky State, geologist and best-selling author, Lanny Ream, is your personal guide to 99 of the best collecting sites in this geographically dramatic and varied region.

An ideal field guide for both amateur and more experienced rock and fossil hunters, each site's write up has an "at-a-glance" info box that tells you what specimens you'll find, the best season for collecting, GPS coordinates, recommended tools and nearby attractions and facilities.

Discover and collect: agates, jasper, gold, garnet, sapphires, geodes/thundereggs, amethyst, fluorite, quartz varieties, tourmaline, pyrite, topaz, trilobites, chrysocolla, petrified wood and more.

All site descriptions also include a brief overview and explanation of the collecting area, a detailed map to the site and photos of what you'll find when you get there.

So grab your pick and shovel and hit the Gem Trails of Idaho and Western Montana!