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List of Rocks, Minerals, and Gemstones Found in Idaho

Idaho isn’t the first place that most people think of when they’ve got rocks on the brain, but it has a far richer geological history than most people think. While the main geological resources of the state are industrial, there are still some really cool stones hiding out among the hills. It’s just a matter of knowing what to look for and where to look.

So, let’s dig right in and I’ll show you a list of rocks, minerals, and gemstones from Idaho!

List Of Minerals And Gemstones Found In Idaho

1. Star Garnet

star garnet in idaho

Star garnets are an extremely rare form of this common gemstone. While garnets are known mainly as deep red gemstones, these gems are cut en cabochon to display their asterism. Asterism is caused by rutile in the garnet, forcing the light to create a four or six-rayed star when it hits the surface of the gemstone.

Star garnets are only found in two places in the world. Unsurprisingly, they’re the state gem of Idaho due to being found in the state. The other place that these garnets appear is in India, making Idaho the sole source of star garnet in the Western Hemisphere.

These garnets are found in the Idaho Panhandle National Forest. Specifically, they’re found in the Emerald Creek Garnet Area. You’ll need a reservation made well in advance but when you arrive you’ll be able to pan through some of the collected gravel and find your own star garnet since collection from the creek bed is no longer allowed.

It’s worth the trip! Check out this brochure if you’d like more details.

2. Opal

precious opal found in idaho

Idaho produces an astounding amount of precious opal, at least for a location in the United States. The small town of Spencer is often considered the capital of opals in North America. While much of it is concentrated in this area, you’ll actually find reports of both common and precious opal from all over the state.

The two biggest mines are near each other. The Spencer Opal Mine is near the town of Spencer, while the Opal Mountain Mine is just a few miles to the northwest. Both of them produce commercial amounts of opal. Currently, the latter is closed, unfortunately, making Spencer Opal Mine the only producer in the area.

Spencer Opal Mine used to offer paid digs. I can’t say that the current deal is worth it entirely, but if you’re in a rush then it might appeal. Their current arrangement is a bit steep, $75 for the day and you get two buckets to fill.

On the other hand, you can also check out some of the other areas in Idaho known for opal:

  • Camas Creek
  • Near Lewiston
  • Little Squaw Creek

Opal shows up in many other locations, so if you’re a local you can just check out Mindat’s map and find somewhere close to you!

3. Gypsum

gypsum found in idaho

Gypsum is mainly known as a valuable resource. It’s used for things like sheetrock for the most part, but it has several forms that may be of interest to a collector. While I’ve yet to see any desert roses emerge from the state, there is a ton of high-clarity selenite available for those who know where to look.

These crystals emerge all over the state in various areas. They can be found in quarries, road cuts, and other locations. Selenite is extremely soft, so care has to be taken while digging it up to avoid damaging the crystals. Much of it ends up being ground for industrial use.

Finding the good stuff can be hard, it depends largely on the area that you’re hunting in. It’s still a common occurrence throughout the state, and high-clarity selenite is known in several different localities.

If you’re interested in finding some, the following areas should be considered:

  • Bannock County
  • Washington County
  • Roadcuts on the 95 Southwest of Midvale

In particular Bannock County and the 95 have excellent samples of selenite, but different forms of gypsum occur across the state.

4. Pumice

idaho pumice

Pumice is a volcanic stone that’s highly porous, and often used in cleaning products and construction. It’s not the first on many collector’s lists, but it’s an important mineral resource for the state of Idaho. It’s found in massive outcroppings.

Pumice is pyroclastic, thrown from a volcano during an eruption. It’s essentially the “froth” of magma solidified. Rapid cooling from sudden air exposure combines with the sudden depressurization of trapped gasses leaving the stone, creating an airy stone that’s composed of volcanic glass. That’s right: pumice is a volcanic glass since it lacks a defined crystalline structure.

Idaho isn’t one of the top two producers of pumice in the US, but it does produce higher quality pumice than any other location. This simply means it has a more even consistency and color, usually bordering on white in the case of the highest grade. Other pumice will run from tan to off-white for the most part.

Gathering samples is easy: visit somewhere near a mine and break off a piece. It’s not something you really have to search for. If you’d like to learn more about Idaho’s pumice, then check out the Idaho Bureau of Mines and Geology report.

5. Petrified Wood

polished petrified wood

Petrified wood is present to some degree across most of North America. Whether it’s the occasional washed-up bit of limb cast in a creek or the petrified forests that can be found in places like Arizona… it’s everywhere. Idaho is no exception to the rule.

The petrified wood of Idaho is mostly of interest as fossil samples, lacking the bright coloration you’ll find in some areas. The interiors tend towards white, brown, and orange shades. Most of the wood is agatized to some degree, making it hard and glassy instead of the more porous specimens found in some locations.

While small pieces can be found in creeks and rivers across the state, most people will want something more substantial. If that’s the case, then you should be looking into visiting Challis, Idaho. The region was covered in volcanic ash after a massive eruption, petrifying large swathes of trees as they collapsed under the weight of the ash. Not to be seen for millions of years.

The two specific regions in the area you’re looking for are Malm Gulch and Spar Canyon. Both of these areas yield impressive specimens of petrified wood and are open to the public.

6. Agate/Jasper/Chalcedony

Agate, jasper, and chalcedony are spread across the entire United States. People will argue all day about which is which, so I just lump them together and leave the precise identification of various local strains of cryptocrystalline quartz to others. Idaho is no exception to the rule and even has a couple of great local varieties of agate to search for.

The jaspers and agates that come out of Idaho can have incredible colors. Anyone who’s active in rockhounding groups on Facebook has probably seen some of the recent finds on private claims in the state. Shocking greens and reds in incredible configurations are pulled from the Earth regularly in the state. There are also the highly sought-after Graveyard Plume agates in their namesake location.

With all of this variety it can be hard to just pick one location. If you’re a local then hunting various creeks and seeing what you can find is a good way to find impressive specimens, just head upstream from your favorite samples and keep looking.

For those who need a place to start, the following areas are all highly regarded:

  • Graveyard Point
  • Owyhee County
  • Succor Creek

Those areas are known to host their own unique varieties, but there are plenty more just waiting to be found on unclaimed land in the state.

7. Aquamarine

idaho aquamarine

Idaho actually has a lot of gemstones in smaller quantities spread throughout its interior. One of these is aquamarine, the blue form of beryl that’s known as a precious gemstone. Samples from Idaho are known to be quite deep in color, including some specimens that are blue enough that calling them aquamarine is a bit hard.

Beryl is a hard gemstone, ranging from 7.5 to 8.0 on the Moh’s scale. This makes it uniquely suited for jewelry, it’s rare that we come into contact with anything which can scratch one of these stones during daily life. The crystals themselves are even more impressive than the gems, in this rockhound’s opinion.

The majority of the great aquamarine in Idaho has been found in the Sawtooth Mountain Range in various cavities in the stones. Unfortunately, this is now considered a wilderness area which makes mineral collection illegal. Only old stock from the location is available.

There are other reputed areas with aquamarine in Idaho, but there’s a lot of confusion about them. There have been false locations written in books (ie: the Centerville location did not produce the crystals claimed) and prospectors jealously guard the few legal areas to collect. 

Finding a legal place to collect will require a lot of detective work, and it may require being a member of the local rocks and minerals club as well.

8. Feldspar

feldspar found in the state of idaho

Feldspar comes in many varieties, ranging from the colored beauty of spectrolite to more “normal” white crystals. Idaho happens to have the latter, but some great examples come out of different geological regions in the state. For those following along, however, please note that Idaho doesn’t contain any of the more exotic variations of feldspar like moonstone or labradorite.

The majority of feldspar in Idaho is of the orthoclase variety. Feldspar’s composition varies since it’s a mineral family rather than a specific type of stone. Orthoclase feldspar contains potassium in addition to the silicate portion of the compound. It’s one of the most common materials found in the Earth’s crust, but it’s not always in a clear, crystalline form.

Variations in Iowa range from clear to yellow crystals for the most part. I’ve seen incomplete reports placing moonstones in Camas County, but I’ve yet to see a visual example of a single sample. Instead, it’s better to focus on areas that have confirmed orthoclase feldspar formations.

The following is just a sample list:

  • Shafer Creek
  • Crystal Butte
  • Lemhi County

These areas all contain decent samples of the mineral, but they’re only the beginning of a much longer list. There are hundreds of confirmed locations with feldspar in Idaho.

9. Garnet

idaho garnets

We touched on star garnets above since they’re a special case, but there are actually quite a few garnets in Idaho if you know where to look. The schist in many places contains numerous small garnets and the occasional gem-quality material is found. The main commercial source is actually in alluvial deposits in a few specific creeks, however, rather than being mined from the rock itself.

A lot of this garnet isn’t jewelry grade, but industrial garnet is an important abrasive. Specifically, almandine garnet is considered the best abrasive for the majority of waterjet cutting where it’s used to create clean cuts in a variety of materials. Idaho garnets are sold by many large jewelry supply houses, so gem-quality specimens aren’t overly rare.

Finding garnets in Idaho is often going to end with panning a creek or stream. Panning for gems is similar to panning for gold, and is often done in the same locales. The denser gems sink to the bottom while sand and dirt come off the top. They’re not as dense as gold, so you’ll want to take a little bit more care, but the concept remains the same. Just pluck the gems out as you find them.

The following areas are major sources of garnet in Idaho:

  • Canyon Creek
  • Emerald Creek
  • Salmon River

These are a good place to begin the hunt if you’ve got garnets on the mind.

Jeremy Hall
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