Garnet is found in Idaho's mountains.
Opal is found in southeastern Idaho. One famous mine is Spencer Opal mine located about 70 miles West of Yellowstone National Park. The mine was discovered by hunters in 1948, and filed on as a mining claim in 1952. The primary formation of the mine is a rhyolite and obsidian flow, full of gas pockets. The opal solution, a silica, was a secondary deposit caused by geyser activity, which settled in the gas pockets. As a result of many eruptions over a long period of time, the opal lays in layers. Most of the layers are very thin, resulting in some of the most brilliant and beautiful triplet opal in the world. Opal information courtesy of A Stone Age
State Gemstone: Star Garnet
Star Garnet was adopted as Idaho's State Gemstone on 1967. When Star Garnet has a 6 ray star (rather than the more common 4 ray star), it is considered more precious than either Star Rubies or Star Sapphires.
Useful Books & Bibliography:
- Roadside Geology of Idaho (Roadside Geology Series) - by David D. Alt, Donald W. Hyndman
Idaho Geology book. There are no better books for roadside geologizing than the Roadside Geology series.
- Yellowstone Ecology: A Road Guide - by Sharon Eversman, Mary Carr (Contributor), David Alt (Editor)
A guide to what can be seen from a car passing through Yellowstone and Grand Teton national parks and adjacent regions of Wyoming, Montana, and Idaho.
- Field Collecting Gemstones and Minerals - by John Sinkankas
Probably the best general description written for the layperson about how, where, and why gem and mineral deposits form.
- Gem Identification Made Easy: A Hands-On Guide to More Confident Buying & Selling New 3rd Edition - by Antoinette L. Matlins & Antonio C. Bonanno
This book is really great for knowing he latest gems, synthetics, treatments, and instruments. Easy to use.
- Simon and Schuster's Guide to Gems and Precious Stones - by C. Ciprianai, Kennie Lyman (Editor), Alessando Borelli
This book is one inch thick and every facing page has a full colored photo of gems or precious stones. Hardness, weights, cuts, refractions, and value of color are given for each gem.
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