You know those cool trilobite fossils? Turns out you can dig ’em up in limestone and shale deposits in places like Ohio, Indiana, Pennsylvania, and New York. A recent speaker at the Northeast Georgia Mineral Society later heard about a limestone cement quarry in Ohio that was just packed with Devonian period goodies – trilobites, shark bits, shellfish, and brachiopods in their gravel. The catch? Whole trilobites were super rare, and finding one was like hitting the jackpot. It actually took him a good three or four trips to the quarry before he finally snagged a complete one.
Fast forward a bit, and when he was at Cleveland State University, he and his buddies went fossil hunting. He and a college friend actually found a bigger one, but, oops, it broke in half! So they each took a piece. And get this – as they were heading out, one of their other friends, who wasn’t even that into fossils, just happened to spot a whole one right near where they parked. Talk about luck!
Now, for a quick geology lesson: Trilobites are these extinct arthropods that had cool exoskeletons and jointed appendages. Think of them as ancient relatives to modern-day crabs, centipedes, spiders, scorpions, ticks, horseshoe crabs, spiny lobsters, and even those little rolly-pollys you find in your garden. Their name, “trilobite,” makes sense when you see them, because the fossil has three main sections: a central spine and two lobes on each side. Trilobites had compound eyes and were ocean dwellers. Scientists figure out what they ate based on their mouthparts – some were probably plant-eaters, while others might have been predators. There are a whopping 22,000 known species of these guys!
Trilobites eventually disappeared during the Permian period, likely due to a massive die-off, possibly from a meteor impact that caused global chaos and volcanic activity. Plus, some folks think another arthropod, the Anomalocaris, might have been preying on them.
Our fine speaker even found some complete specimens in the shale deposits of the Conasauga River in NW Georgia once. It was near a new neighborhood, and he found tons of different species! But, sadly, word got out, and collectors started parking all over the neighborhood, which led to the site getting shut down and blocked off. It’s a real reminder for collectors to always be super respectful of these awesome locations. Oh, and if you’re looking for more trilobites, you might have some luck in Tennessee and Kentucky, too! Enjoy these photos of trilobites fossils from Georgia and from Madagascar, and enjoy the educational slides and feel free to share!
From our recent new homebase in North Georgia, let’s talk about the Blue Ridge and the Piedmont lands and the geology and minerals of North Georgia. We’ll look at them together, seeing as how the rocks there, the ones that got squeezed and heated up (that’s metamorphic, you know) and the ones that bubbled up from the earth like old volcanoes (igneous), well, they’re cut from pretty much the same cloth.
Now, the old-timers figure that way back yonder, the whole shebang of North America bumped right into this big ol’ landmass called Gondwana, and that’s how they got Pangea, this super-duper continent. That mighty clashing of the earth’s plates, it caused all sorts of cracks and wrinkles in the Blue Ridge and Piedmont here in Georgia. And all that pressure and heat? Why, it just folded and lifted those rocks right up.
The Blue Ridge Mountains, bless their hearts, they’re some of the ancientest hills you ever did see, a whole lot older than those young whippersnappers out west, the Rockies, and even them big fellas over in Asia, the Himalayas. When the Blue Ridge first poked their heads up, they’d have been some of the tallest things around, I reckon. But then the rains came, and the floods, and they just washed away tons and tons of rock and dirt down into the lowlands, the plateau, and even further out. Some folks who study rocks have even found bits of that old wash way out in Arizona, in the Grand Canyon!
Later on, that Pangea thing, which included these very Appalachian Mountains, well, it got all torn apart by more of that earth movin’ and shakin’. Scientists have found pieces of these same Appalachians way down in South America, over in northwest Africa, and even in Greenland, Great Britain, and Europe. But nowadays, all that’s left standin’ here are the tough old cores of these Appalachian rocks.
Now, up in northeast Georgia, them Blue Ridge Mountains make up the highest ground in the whole state. Here in Georgia, these rounded ridges and worn-down peaks go from about sixteen hundred feet up to nearly forty-seven hundred feet above sea level. The whole Appalachian chain goes even further, roughly from Alabama all the way up to New York.
The Blue Ridge, they’re known for that pretty blue haze that hangs over ’em, and for their mighty steep gorges, canyons, and waterfalls. Take Tallulah Gorge, for instance, down there in northeast Georgia. It’s a good six hundred feet deep, making it the fourth deepest canyon east of them Rocky Mountains. Mighty impressive!
Now, the southern edge of the Blue Ridge is near this thing called the Brevard Fault Line. Right on the other side of that line, you got the Piedmont, and it’s made up of some mighty old rocks too. The story goes that these rocks started out as just plain old muddy clay that settled way down deep in the ocean. Seems like mud gets carried the furthest from land that’s wearin’ away, mixes in with some sand, and then just sinks to the bottom of the deep blue sea. Then, when that mud gets squeezed and heated up (that metamorphism again), it turns into mica. And as most folks around here know, Georgia’s got plenty of that sparkly mica.
The rockhounds have also found a lot of this stuff called Metagraywacke, which is just sandstone that’s been changed by heat and pressure. Graywacke, that’s what they call the stuff before it changes, forms in layers of clay and sand that got sorted out in deep water with strong currents. The bigger bits of gravel and sand sink to the bottom first, and then the finer stuff settles on top. Over time, all that gets cooked and squeezed, and out pops Metagraywacke.
Now, there’s all sorts of different metamorphic rocks and minerals in the Blue Ridge area. That’s ’cause it’s been through a whole bunch of episodes with different amounts of heat and pressure and foldin’. Along the western edge of the Blue Ridge, where things weren’t quite as intense, you find slate and phyllite (some folks call it fillite). Then, as you go further in, you find minerals like chlorite (that forms at around two hundred degrees Fahrenheit), shiny silver muscovite, black biotite, garnets, and staurolite. And over on the eastern side, where things got real hot and squeezed tight, you can find kyanite (that takes about eleven hundred degrees Fahrenheit to form!), sillimanite, andalusite, some pretty zebra-striped gneiss, and even migmatites.
And that ain’t all! We got copper, marble (that used to be limestone, like around Tate), talc, this old blue quartz meta-granite (got its color from titanium), quartzite rings around Tallulah Dome, and even some of that igneous granite in the Blue Ridge. Why, even Mount Yonah over in White County is made of this granitic gneiss. It formed way back when molten granite pushed its way up into layers of metamorphic rock.
Now, one more thing you’ll find in both the metamorphic and igneous rocks of the Blue Ridge and the Piedmont is quartz. It can form when hot, watery stuff full of silica pushes into cracks in the rock and makes veins. And gold? Well, gold can be found in those same kind of veins, along with quartz and some other minerals like pyrite. In fact, if you see quartz veins that are stained with iron, that can be a sign that there might be gold nearby. Them gold deposits in the Blue Ridge led to the first big gold rush in America, right around Dahlonega, Georgia. Read our review of the Dahlonega Gold Museum here: http://www.americangeode.com/blog/dahlonega-gold-rush-museum-review/. You can also find a little bit of gold scattered in those igneous granites, but most of the gold folks have dug up over the years came from what they call placer deposits – that’s just old river and stream gravel that’s been worn away over time.
Remember to #getoutandrockhound and share www.americangeode.com with your rockhound friends!
Knoxville Gem & Mineral Society 2021 Annual Gem Show
Rothchild Conference Center 8807 Kingston Pike, Knoxville, TN 37923
Friday, October 15, 10:00 am – 6:00 pm Saturday, October 16, 10:00 am – 6:00 pm Sunday, October 17, 11:00 am – 5:00 pm
As a precaution for Covid masks will be required for admittance.
The show will feature 23 vendors with a wide variety of jewelry, fossil and mineral specimens, meteorites, gemstones, and decorative objects. There will also be educational activities and gem and mineral ID tables. Admission Adults: $6.00 Run of Show Pass: $10.00 Children Under 12: Free
Through one of the gem and mineral clubs to which we belong, we were invited to rockhound for lace agate, banded agate, moss agate, and druzy quartz from a private mining site near Summerville, Georgia.
I arrived and was lucky to have the entire mining area to myself except, over the course of the morning and afternoon, 2 different couples stopped by to collect agate, and a family was out on a rockhounding trip.
American Geode takes that attitude that if you can, take a lifetime supply. We filled up every bucket and bin we brought, and also picked up many large and heavy agates. The stone was plentiful. The only time we used our tools was to break apart a behemoth stone into more manageable sections. We found moss agate, lace agate, banded agate, and our favorites had druzy quartz pockets.
The beauty of these stones were not easy to see without being splashed with a little water, but we ran out of water, so started collecting more than enough to overcompensate as we expected to have some stones better suited for the garden. On a recent gem and mineral meeting over Zoom, when I was showing off these fine agate specimens, I learned that the agate, and the stone formation containing covers a lot of Northwest Georgia, even into Tennessee, but it is on private land, or federal park land, so not available or accessible to the general public.
This agate tumbles well, but it loses a lot of surface area during the tumbling. It is beautiful however, and we are sure that a cabochon or lapidary person would have even more fun with this agate.
We have been tumbling North Georgia river stones, and most recently the Summerville Agate, in a 20lb barrel from MJR Tumblers. Each stage of tumbling takes about a week, and at the conclusion of each tumbling stage, I have been dumping the grit and the agate and river stone grit into the flower garden. The flowers LOVE IT! The rose bushes are more plentiful than ever before, and deeper colors than they were last year. One small rose bush that was red last year, was almost tie-dyed looking with streaks of white. The red impatiens are now a shade of orange. The mint and parsley plants are overgrowing! While this is not fertilizer, I can only guess the plants appreciate this concentrated mineral content in the otherwise mostly red clay soil. After I do dump the tumbling grit sludge into the garden I dilute it, and that happens naturally because I need to clean the tumbling barrel before the next stage, and also need to rinse thoroughly the stones before starting the next tumbling phase, or polishing phase, so I am hosing down the barrel and stones over the garden too, and that helps dilute the sludge and make it run over more of the garden to be soaked up. I am sure that the sludge mix from a cabochon workstation would have the similar effect on your outdoors flowering plants. Never dispense of tumbling or cabochon grit down a drain, and no never, dispense of that valuable mineral sludge, but add it to your garden. For any questions about gardening, or rock tumbling, feel free to contact Charles at charles@americangeode.com.
