Maryland isn’t the most geologically diverse area, but there’s a lot of cool stuff hiding in the area. You just have to know what’s there and where to look to make the most of it, especially in such a small state. For those visiting or living there, a heads-up is a good way to know what you’re missing out on.
So, let’s get to it with a list of rocks, minerals, and gemstones found in Maryland!
Calcite is among the most common minerals on the planet, taking on a wide array of colors and different crystalline forms. For the most part, it can be found in some form or another across the entire planet, it’s usually just the larger and more interesting varieties that we’re interested in. It’s one of the many forms of calcium carbonate that we find in the world of geology.
Calcite is a strange mineral for collectors. After all, there are tons of forms and most of them are centralized in local areas. What two collectors think of as “calcite” may barely resemble each other once you get past the innate physical qualities of the mineral like hardness and crystal structure.
Calcite from Maryland is generally yellow to orange in color, and formations are usually made of smaller crystals spread across the host rock. On occasion, you’ll also find larger single crystals of the mineral but they’re not nearly as common. It’s spread across the state with heavy distribution, making it one of the more common interesting minerals of Maryland.
You can often find calcite in quarries and road cuts in the state. The best examples seem to come from quarries in Baltimore County and Carroll County.
There’s still wide distribution, with over a hundred known sites in the tiny state, but those counties seem to produce many of the best samples.
Garnets are a varied family of gemstones, but most of us know them as bright red. That’s not strictly the case, there’s everything from the purple of rhodolite garnets to the deep, shocking green of tsavorites spread across the family. They all have the same base chemical composition, but there are a number of families of garnet.
Garnets are often spread in mica, a flaky stone. In Maryland, the primary type of garnets found is grossular. These garnets range from yellowish orange to red to brown depending on the impurities held in their crystalline lattice. They occur in both small clusters and as single crystals spread through the host rock.
The majority of the garnets will be held separately in the host rock. Finding pieces of this is simple if you know where to find the right outcroppings. Some clusters are also found in the state, and occasional small crystals are pulled from stream beds in the surrounding areas through panning.
If you’re looking to add some Maryland garnet to your collection then the following areas are good places to check:
- Montgomery County
- Baltimore County
- Area around Cardiff
While rare, there are some great examples of this mineral in the state for those with the persistence and luck to find them.
Tourmaline is a varied gemstone, with the most commonly known variety being the pleasing crystals known as Watermelon Tourmaline. It can also rival the best-colored gemstones when it’s found with the right impurities and configuration. That said, the majority of the stone is schorl, which is an opaque black tourmaline subtype.
The most common place to find tourmaline is in pegmatite stones close to granite outcroppings. Pegmatites are best thought of as massively grained stones, with large chunks of the constituent mineral mixed into a conglomerate. These pegmatites are a rich source of many crystals, and almost all of them contain tourmaline.
Of more importance to the collector is the fact that tourmaline is associated with the chromium mines in Maryland. This leads to the formation of chrome tourmaline, a deep green crystal with the iconic tourmaline form. The best are almost indistinguishable from emerald! Chrome tourmaline found in Maryland tends not to be of gem quality, but it still makes for impressive specimens.
While tourmaline can be found in granite outcroppings and associated pegmatites across the state, the best samples seem to come from Chrome Hill but the tailings and piles of all of the chrome mines in the region seem to occasionally bring some tourmaline to light.
Pyrite is an iron sulfide mineral, a combination of elemental iron and sulfur. Despite the makeup of the stone, it exhibits a brassy color and is often associated with gold in nature. Most people know the name “Fool’s Gold” is associated with pyrite for that reason. Jokes on them, of course, since pyrite can actually contain a considerable amount of gold trapped in its crystalline form.
Pyrite is a common mineral, but well-formed crystals are a bit rarer. It forms into cubic, golden crystals that look great and it’s often associated with other interesting minerals like quartz and albite. Most of the time it’s found as smaller crystals, even single crystals spread across host rock.
There’s nothing truly special about the pyrite samples from Maryland, other than the fact that they’re pyrite. It’s spread across the entire state and occasionally good samples are found, but most are more of a trace on other minerals. It’s still worth a shot for the dedicated fans of iron pyrite.
The following areas are known to host pyrite:
- Around Cardiff
- Mahogy River
- Bare Hills Mining District
You may have to put some effort into finding great samples, but it’s well worth it to add a hand-collected bit of pyrite to the shelf.
The other big thing they’re known for is being the main source of asbestos. Chrysotile fibers were used in the majority of asbestos products, the exact same ones that have caused late-night TV to be inundated with commercials about mesothelioma. Extra caution, including a respirator rated for asbestos, is a strongly recommended quality for lapidaries looking to cut this stone.
Serpentine is a group of minerals that are known for a few things. The first is as a decorative stone, where the pleasing and mottled olive green appearance has made it a favorite for years. You can still find serpentine cut to fit jewelry, although it’s rarely used as a base for art objects made with precious metals these days.
There’s a lot of this stone in Maryland, but most people are more concerned with special varieties. Antigorite and its subtypes Williamite (a dark green, transparent serpentine) and bowenite (a very hard, compact form of the stone) is of interest to lapidaries. Williamite is comparable to nephrite jade when it comes to hardness, coloration, and its ability to take detail.
While serpentine is all over the place in this state, the following areas have the better stuff:
- Soldier’s Delight Ridge
- Low’s Mine
- Bare Hills Mining District
Since a lot of it is found around old mines, you should always study the area as much as possible to avoid the various dangers inherent to that kind of area.
The various cryptocrystalline silicas that make up the majority of collectible rocks are present in Maryland in their own distinct forms. We’ll cover the unique “agates” in the next entry but occasional washes from other regions bring in different agates at the borders of the state. Maryland’s earth actually isn’t known to host any agate but the other two forms are abundant.
Jasper in Maryland tends to be of the less interesting variety, largely just red in appearance with minor coloration. It’s attractive but not particularly unique compared to jasper from other regions. This jasper was used for arrowheads in the past. There is also botryoidal chalcedony to be found, appearing as nodules of roughly spherical white stone.
All three of these stones are made up of the complex intergrowth of two polymorphs of silica; quartz and moganite. They interlock on a tiny level, leaving a stone that feels like glass in the hand but actually does have a crystalline structure. It’s just so small you’ll need a powerful microscope and an incredibly thin slice to make it out.
For those looking in Maryland, the following areas are ideal:
- Baltimore County
- Soldier’s Delight Quarry
- Bare Hills Mining District
But some examples can be found across the entire state.
7. Patuxent River Stone
While broadly (and falsely, we’ll touch on that in a moment) known as agate, these are also the state gemstone of Maryland so they deserve their own heading. Patuxent River Stones are red, orange, and yellow nodules that are often found in rivers throughout the state. Their main distinction comes from their color, which matches the state flag.
The naming of Patuxent River Stone as the state gem is… kind of embarrassing. Information was unforgivably terrible for such a recent development including describing the stone as “agatized dinosaur bone” at one point. Those familiar with gem bone are probably scratching their heads over that one.
So, what are these mysterious stones? Iron-colored quartzite is a far less fascinating description than Patuxent River Stone. They’re a bit too common to really be called a gem in most people’s estimations, but it can still be good fun to pull some from streams and rivers.
If you’re looking to get in on the action, you’ll need to find a place suitable for collection along the Patuxent River. The stone is mainly associated with old sandstone quarries, which can provide insight into where to look.
Amber isn’t really a mineral but it’s long been considered a gemstone. Amber was originally deposits of sap and resin from ancient trees, often trapping insects, plant matter, and even the occasional small vertebrate before ending up underneath the earth. Over time the resin becomes polymerized, creating the stone known as amber.
The most well-known form, Baltic Amber, often shows up on shores but some amber is dug out of the ground. That’s the case in Maryland, where the stone is contained in seams of lignite coal. These coal seams are formed from ancient plant matter crushed and heated over time and created a safe place for the amber to hide.
The lack of pictures of samples is a bit telling. The majority of amber isn’t the clear kind you picture from Jurassic Park. Instead it’s heavily included, borderline opaque, and often jammed full of random bits of stuff from the past. Still, it’s there for those who are willing to look.
Your best bet is to find exposed coal seams along the Eastern Coast of Maryland. It’s known to show up at both North Ferry Point and Sullivan Cove for those who are willing to look for samples. It will be an adventure, Maryland amber is very rare.
Quartz shows up across the planet. It’s probably the most famous type of crystal, having become the generic “crystal” in media and our imaginations. It’s formed of silica, one of the most abundant minerals in the Earth’s crust. There are many variations of quartz, the most well-known being amethyst and citrine which are both colored by iron in the color centers of the stone.
In Maryland, quartz is primarily seen as river tumbles from regions to the North. These will be rounded, opaque, and white. They may be clear once you polish them. You’ll see this type of quartz referred to as “milky quartz” on occasion as well, but true milky quartz has inclusions that cause the cloudiness instead of just surface damage making it appear cloudy.
There is also a small amount of smoky quartz in the region. This is dark-colored quartz, ranging from deep brown to deep grey in color, that is also colored with iron. It’s closely related to amethyst and citrine, but neither of the latter two seems to appear in this state.
If you’re looking, then the following areas are a good idea to check out:
- Hunting Hill Quarry
- Baltimore County
Anywhere associated with the old chrome mines is also a good spot to check.