* Coal (the state mineral of Kentucky and the state rock of Utah) is not a mineral, but a fossil fuel. Petrified wood (state gem of Washington and state stone of Mississippi) is neither a gem nor a stone, but also a fossil.
**Michigan state "stone" (petoskey stone) and Florida state "stone" (agatized coral) are actually fossilized corals.
***Hawaii state "gem" (black coral) is the skeleton of a marine animal.
by Smithsonian Handbooks -Review: Well written and informative. The author is very knowledgeable, the book itself is very interesting and easy to understand .. more
The National Gem Collection by Jeffrey E. Post (Smithsonian Institution) 5 star Review: The Smithsonian Institution's Museum of Natural History holds the world's greatest collection of gems ... in this beautiful book Dr. Jeffrey E. Post, curator of the National Gem and Mineral Collection ... more