This article covers a variety of different areas in Idaho where you can find fossils. Please note that some of these areas do allow collection for personal use, but many areas are off-limits to collecting! I am going to include these locations to make this a good comprehensive list, but please be aware of any potential restrictions.
For the serious rockhound, I always like to let people know that there are countless sites where fossils exist that will never be on any “list” and probably never will be. Prehistoric animals were everywhere. Fossils exist because conditions were just right and allowed for their preservation after they died. Some areas were better than others and they comprise many of the locations listed here. Other areas will require more research, study, and boots-on-the-ground to find them. You might be surprised what is out there if you get out and look.
Clarkia Fossil Beds
This is one of Idaho’s better fossils sites. It is located near the town of Clarkia in Northern Idaho, and has some exceptional leaf fossils that date back 15-million years. If you visit the area, check out nearby Emerald Creek, where Idaho’s famous star garnets are found.
Hagerman Fossil Beds
The states most famous fossil site is definitely the expansive beds located in Hagerman. Over 200 different animal species have been identified here. A complete skeleton of the Hagerman Horse is on display at the visitors center. There is no digging allowed here, but its definitely worth a visit to learn about this unique fossil site.
This fascinating limestone cave is located in southeast Idaho near Bear Lake. It is over 1/2 mile deep and is full of amazing stalactites and stalagmites. Just exploring the cave is worth the visit itself, but fossil lovers will appreciate that there is also lots to see. This was once a warm water environment which harbored various coral species. Evidence of these ancient critters can be seen throughout the cave.
Tolo Lake Wooly Mammoth
Perhaps the most impressive single fossil find in Idaho history would have to be the discovery of a complete wooly mammoth near Tolo Lake near Grangeville. The find was made by state workers in 1995, when a huge bone was spotted while doing work at the lake. Further excavation resulted in a complete skeleton! A total of 3 wooly mammoths and 1 early bison skeletons were recovered from the site. There is a complete replica of the mammoth on display along the highway just outside of Grangeville.
Malm Gulch Petrified Forest
Another place where you can take a glimpse into the past is at Malm Gulch just south of Challis. Here you will find an ancient petrified forest that once existed. 50-million years ago, the climate was much more like you would see along the Pacific Coast. Large coniferous trees grew. Now, the area is a desert, but a few petrified tree trunks still exist.
The Undiscovered Fossil Sites
I have to emphasis once again that fossils can be found just about anywhere. Road cuts and quarries are two locations that can be worth exploring because they dig down into the deeper soil layers. You might be surprised how many good fossil sites are located right along the roadside.
I grew up in southern Idaho, and while exploring the desert it was not uncommon to find ancient reefs that were full of invertebrate fossils. I know of two locations that I have never seen any evidence of any digging or collecting at the site. There are ancient reefs all across the southern Idaho desert.
Petrified wood is even more abundant. Keep your eyes peeled when you are out on a hike. You’d be surprised how many good pieces are out there sitting right on the surface waiting to be discovered. Nicer material can be cut for lapidary purposes, and smaller pieces can be put into a rock tumbler to expose their natural beauty.
A friend of mine who worked for the BLM found an interesting bone in Owyhee County about 10 years ago. It was identified as a vertibrae of a giant mastodon. This is an area where you would never expect to find such an amazing fossil. You truly never know what you could find out there!
Fossil Collecting Laws in Idaho
As I already mentioned, some of the more well-known sites are amazing places to explore and see fossils, but some are off-limits to collecting as they have been set aside for research. Other sites do allow collection with simple hand tools for personal use. You need to do further research before you visit to see if you are allowed to collect.
If you are looking specifically for sites that you can do some digging for yourself, I recommend getting a good book like Gem Trails of Idaho or Rockhounding Idaho for some specific collecting sites with directions.
As with any type or rockhounding or mining, you need to know who’s land you are on. Private lands, state, federal (BLM, Forest Service, National Parks, etc.) will all have different rules.
Generally, on BLM and Forest Service lands (which covers 2/3 of Idaho) you are allowed to collect modest quantities of invertebrate fossils (corals, leaf plates, snails, mollusks, etc.) for personal use. These specimens cannot be sold for profit. Petrified wood can be collected up to 25 pounds per day, plus 1 larger piece. A total of 250 pounds can be collected in a year.