Indiana may not be at the top of your mind when you’re thinking about rocks and minerals, but there are some interesting pieces to collect scattered across the Hoosier State. While many of these resources are primarily industrial in nature, there are still quite a few places that may interest prospective rockhounds.
So, let’s break into it and I’ll show you a great list of the rocks, minerals, and gemstones found in Indiana and give you some tips on where to look!
Minerals and Gemstones Found In Indiana
Calcite is among the most common crystals in the world. It’s a relatively simple mineral, just calcium carbonate, but it actually forms in a variety of different forms. Calcite is often sold based on its crystal structure or its color. The provenance of samples is important to finding something attractive. It’s found in geodes, on other crystal formations, and growing by itself on rare occasions.
Calcite often contains microscopic fossils, including those of things like diatoms and zooplankton from ancient seas. These can be found using a microscope in some cases, but they don’t make up every piece of the mineral.
Calcite can be found spread across the entire state for the most part. The variety found in Indiana is often brown or yellow with high clarity, but clear, well-formed crystals also emerge at other times. There seems to be little to no presence of more brightly colored samples in the region, unfortunately.
If you’re trying to find calcite in Indiana, one of the following areas is a good way to start:
- Near Huntington
- Near Elizabethtown
- Harrodsburg Road Cuts
These are just a few of the many locations in the state that happen to have calcite.
Limestone is a sedimentary stone comprised of mixed aragonite and calcite in small crystals. The result is a white-to-off-white, crumbly, soft stone that most of us can recognize at first glance. Limestone is actually a major resource for Indiana since it can be ground up and used in various chemical processes. It’s also been used as a building material at various points in our history.
The formation of limestone that’s important in Indiana is known as the Salem Limestone. It’s a variety that’s found in the central portions of the state, and it was of huge importance for the construction of monuments and buildings in the past. American architecture heavily featured limestone in the past.
The stone isn’t used frequently for this purpose anymore. It turns out that even rain isn’t what it used to be. While “acid rain” will recall horrors for some people, the main problem was actually with architecture. Limestone is extremely vulnerable to low-pH liquids, even vinegar can damage it heavily with a few moments of contact. The formations are still out there, however, even if the demand for the stone’s use in buildings is not.
Indiana limestone is found between Bloomington and Bedford and is still considered one of the finest limestones available worldwide.
Iron sulfide makes up both of these interesting minerals. The only difference is the charge levels of the iron ion included in the makeup of the mineral. Both show up as cubic crystals in various locations across the world, creating glossy brass or silver mineral samples. Marcasite is a bit more fragile, being more brittle and prone to breaking.
Pyrite has been known as Fool’s Gold for a long time. It’s often found alongside the minerals and stones that contain gold-bearing ore and its similar color made it easy for new prospectors to mistake it for something else. In a twist of fate, it turns out that pyrite can actually contain a decent amount of gold locked up in its matrix. Up to .25%!
Marcasite is best known as a mineral sample. Some agate fans will recognize it as one of the compounds that make up plume agates. In the case of marcasite, it will create a silver “plume” with geometric details. It’s collected both on its own and when found as an admixture with other crystalline compounds. It occurs in most of the same areas.
If you’re looking for pyrite in Indiana, the following locations are known to bear it:
- Near Huntington
- Parke County
- Near Logansport
Pyrite is a relatively common find in Indiana, so if the above locations aren’t near you then you may still be able to find a place to hunt.
Fluorite is the first love of many rock collectors. The commonly available Rainbow Fluorite specimens on the market have gained a life of their own, even if the majority of material doesn’t have quite the same visual flash. Of course, all of it has an excellent flash underneath the light of a shortwave UV lamp.
Fluorite from Indiana tends to be a bit on the boring side. Transparent and well-formed is about the best you can hope to find on a regular basis. There is some golden-colored and brown material available as well, often looking just a bit like a dirty crystal. This means the samples from the area are mainly important for industry.
Fluorite is used as a primary source of fluoride for many chemical reactions. That’s very valuable for chemists and it’s one of the main reasons the mineral is harvested in large quantities. The fact that some of it happens to be pretty is just a side effect of various impurities. Chemically pure fluorite forms as cubic, clear crystals.
For those who want to find a sample of their own the following areas are good to check:
- Lawrence County (Geodes)
These areas and the quarries around them all host fluorite.
The macrocrystalline form of silica, quartz is one of the world’s most iconic crystals. Not only is it the stuff our common crystal points are made of, it’s also the same base mineral as many fascinating gemstones. Amethyst, citrine, prasiolite, and others are all formed from quartz with various elements contained in their crystal structure.
Quartz is found in geodes, as clusters, and sometimes as rounded rocks worn by their travels along waterways. It’s a simple mineral, almost entirely inert. Silica itself makes up the majority of our planet’s crust, and it can also be found in other common gemstones like agates and jaspers. It really is one of the basic building blocks of our world.
Quartz can be found as both loose crystals and contained in geodes in the state of Indiana. The loose crystals are generally parts of old vugs that have eroded out of the limestone they’re hosted in. The vast majority of quartz comes from these hollows where ancient quartz formed, making it relatively easy to find in many cases.
The following locations are all known to host quartz in Indiana:
- Road Cuts near Brown County State Park
- Lawrence County (Geodes)
- Salt Creek
There are many more places it can be found in the Hoosier State, just keep your eyes peeled for limestone bedrock.
Celestine, celestite, or whatever you’d like to call it is a fascinating blue mineral that contains the rare earth metal strontium. The exact chemical formula is strontium sulfate (SrSO₄). These colors range from strongly colored to only light blue. The samples from Indiana tend to be on the latter side of things, forming with pale colors.
Not all celestine forms in this way, however. There are formations that much more closely resemble the limestone stalactites and stalagmites many people are familiar with, rather than forming as crystals or in hollows as geodes. This is best seen in Crystal Cave in Ohio.
Celestine is found worldwide, but usually in small amounts. While it’s scattered across a few areas in the state it’s not as easy to find as many of the other minerals on this list. Be prepared to spend a good amount of time digging around to find any samples, let alone good ones.
It’s still worth a shot, so try the following places:
- Lawrence County
- Near Spencer
There are other scattered deposits that aren’t as well known, but the two locations above are definite localities for the pale blue stone.
Sphalerite is a primary ore of zinc, often associated with the lead ore galena when found in nature. It’s the most commercially important ore of the white metal. Zinc is actually used in a surprising amount of things we encounter or use on a regular basis. For instance, zinc is part of the alloy that makes brass. It’s also the metal that coats corrosion-resistant galvanized steel… and why welding any kind of galvanized steel is so hazardous!
Sphalerite itself is a simple sulfide, zinc, and sulfur combined to create crystals. These crystals often have high iron content, leading to the association of sphalerite with black, cubic crystal formations. Sphalerite with higher purity often appears as yellow, transparent crystals instead.
The sphalerite contained in Indiana varies greatly in quality. Pure, nearly white crystals are found at times while in others it’s the classic, glossy black formation of low-grade, high-iron sphalerite. It’s actually a common find across most of the state but concentrated in a few areas where it’s used for commercial production.
The following locations are associated with sphalerite:
- Lawrence County
- Allen County
- Near Bloomington
Sphalerite isn’t hard to find in Indiana, it’s just a matter of finding a piece that you like.
Indiana is another of the many states that contain gold. While it’s not present in commercial amounts, there’s more than enough material left for prospectors. Panning or sluicing the gravel of rivers and creeks across the state produces small amounts of gold, just don’t expect to find a mother lode hiding in the hills.
Gold is one of the most important minerals to human development. It’s been used as a currency for almost all of human history. As a metal, it lacks many of the properties we want for tools, but it makes up for it in other areas. The unique color, high shine, and virtual inability of gold to corrode all added to its value and made it immediately recognizable.
So far as I can tell, all of the gold in Indiana is spread in creek beds. Leftovers from the ancient journeys of giant glaciers as they crept across the state and left behind alluvial deposits of gold and other minerals and gemstones. It’s worth it to buy a pan and head out to the nearest creek if you live in the state.
On the other hand, some spots are known to be much better than others. The following places are all considered above average:
- Salt Creek in Brown County
- Morgan County
- Monroe County
While the above areas produce most of the recreational gold that prospectors find, it appears that many of the creeks in Indiana have some small amount of gold contained in the gravel, sand, and silt that makes up their bottom.
Dolomite is what happens when you add a bit of magnesium to the mixture that produces calcite.
It’s most often seen as a simple stone without much distinction, but it also forms interesting crystals in its own right. Dolomite formations are sometimes found mixed with other stone formations, especially shale.
Dolomite is something like limestone but it’s far more resistant to weather and acids. Indeed, Niagra Falls is produced by differing erosion levels between shale and dolomite, with the shale having long since been eroded and leaving behind the Niagra escarpment.
The dolomite found in Indiana is largely dolostone, which is the name for dolomite dominant stones. However, in certain areas crystals of the mineral are found. These form both as geodes and in hollow vugs, just like quartz and calcite do in this area. While resistant to erosion, dolomite certainly isn’t immune and it’s easiest to find as a crystal when it’s still in the host rock. Areas like road cuts are the best places to look.
Dolomite crystals are known in the following areas:
- Monroe County
- Harrison County
- Near Corydon
Dolomite is deserving of a place in most mineral collections, and it’s found easily enough as long as you’re in the right locations in Indiana.
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