Search the Community

Yesterday I was able to take a trip to the Silurian Racine formation of Southern Wisconsin. This site was easier than others due to the clear stratification, and I was able to see some of the reef overlay and underlay. finds included: my first dolomitized crinoid calyx, a nice fez-looking coral, some Bumastus trilobits, and what looks like a Cornulites impression? I’m curious if anyone has thoughts on the circular impression with calcite growths in it- unsure if it‘s an imprint or just a gap with mineral growth. Included a fun extra picture of old and new critters paired together.

Most people are familiar with the Conasauga Formation when they think of Georgia's Cambrian record, but the Peach State has a paleontological history dating back several million years before the Conasauga was deposited. Indeed, the oldest fossils in Georgia date back to the early Cambrian, and consist of a diverse form of worms, brachiopods, trilobites, and other creatures such as hyoliths and archaeocyathids. This early Cambrian record is largely divided into three formations, from oldest to youngest the Weisner Formation (part of the Chilhowee Group), the Shady Dolomite, and the Rome Formation. All of these formations, as well as the overlying middle Cambrian rocks of the Conasauga Formation, are well exposed in the Rome and Cartersville areas. Cartersville is a mid-sized town in North Georgia with a rich interconnection between history and geology. Situated near the confluence of three major geological provinces (the Valley and Ridge, the Blue Ridge, and the Piedmont), the Cartersville area was uniquely positioned for the discovery and future development of a variety of mineral resources. Wide scale mining began in the mid-19th century with the establishment of the Etowah Iron Works along the Etowah River. Although the bulk of the works were destroyed by Union forces during the Civil War, mining not only continued in and around Cartersville but actually expanded in the post-war period. Iron was the principal product for a while owing to the region's rich limonite deposits, but by the turn of the century ochre and barite production also became prominent, if not more so. Mining operations peaked by the middle of the 20th century, but some active mines remain in the area, and they continue to be a favorite with mineral and fossil collectors. Thankfully, this past history of mining, combined with the recent construction due to Atlanta's explosive growth, has exposed rocks typically left buried under the thick clay and vegetation of North Georgia. The Shady Dolomite was, and still is, the focus of the brunt of the ochre mining around Cartersville. A carbonate unit, the Shady is easily weathered in North Georgia's humid and rainy climate, dissolving much of the rock and underlaying the ground in a thick, reddish clay. Due to the nature of the weathering, however, distinct beds can sometimes be seen in cuts made into the Shady, as shown in the above photo from a construction site in Cartersville. Another exposure of the red clay residuum made out of weathered material from the Shady Dolomite. Although the carbonates of the Shady are frequently weathered into a thick, red muck, this weathering process typically uncovers a wide variety of rock types that are more resistant to chemical attack, and which would have otherwise been locked into the dolomite. At exposures like the one above, pieces of shale, iron oxides, and chert are common. Alongside the chert are fossils from some of the oldest reef communities in Georgia. This small piece of rock contains fragments of archaeocyathids, ancient sponge-like organisms that once established reefs in the early Cambrian sea. Alongside archaeocyathids, other fossils like trilobites and brachiopods are sometimes found in the Shady, but I didn't find any personally. Aside from iron and ochre, Cartersville was an important center for barite mining around the turn of the century. Most barite mines were located east of town, near the contact between the Valley and Ridge and the Blue Ridge provinces. Although most have been filled in or flooded, one pit that is still left can be seen at Pine Mountain east of town. A few pieces of barite ore line the trail leading up the mountain. A small piece of barite ore from near Cartersville. The walls of a former mining operation near the base of Pine Mountain contrasted with an image of a similar mine when in operation. Leading up the trail at Pine Mountain, one travels across geologic provinces. The valley floor is underlain by rocks of the Shady Dolomite and Rome Formation, part of the Valley and Ridge province, while Pine Mountain itself lies within the Blue Ridge. Climbing up Pine Mountain, you begin to sense that change reflected in the rocks underneath you. The red clay and chert residuum of the Valley and Ridge gives way to brown and white dirt, and the chert and dolomite boulders give way for quartzose sandstones, quartzites, and schists. Along the trail, numerous pieces of quartz sandstone from the Weisner Formation are exposed, and in these boulders you can sometimes catch glimpses of the earliest recorded life in Georgia! The picture here shows a sandstone boulder with a couple of well-worn Skolithos linearis worm burrows. Whereas the Shady Dolomite was deposited in a shallow, tropical sea, the upper Chilhowee Group was deposited in a near-shore environment as indicated by the coarse sediment. That means that 530-550 million years ago, during the early Cambrian, what is now a mountain would have been a warm, sandy beach! And, although they may not seem like much, the humble tubes in the rock illustrate a time when life was not everywhere abundant, and the diverse lifeforms we find at beaches today had yet to appear. Climbing the rocky trail to the summit, one is well-rewarded with a view of the entire Cartersville area, including a view across much of the Piedmont to Kennesaw Mountain beyond, and across much of the Great Valley to the Armuchee Ridges. One can also get a sense of the legacy of intense mining that took place around Cartersville from the many red-colored pits scoured into the nearby hillsides, ghosts of operations past and present. On top of all of that, one can also visualize the impact geology has on the topography of an area. Being the intersection of so many geologic provinces, the Cartersville area is marked by numerous faults, folds, and other complex structural geology that has left pockets of one formation nearly surrounded by pockets of another. This has contributed to the hilly nature around Cartersville, as the comparatively resistant rocks of the Rome Formation and Chilhowee Group forms island-hills in the sea-valleys of the Shady Dolomite. The view from Pine Mountain. The red areas are current and past mines around Emerson, Georgia, just south of Cartersville (which includes the buildings in white). The hills here, which make up part of the Allatoona Mountains, are held up by resistant units like the Chilhowee and Rome while the valleys are underlain by softer carbonates like the Shady. On a clearer day you could make out the Armuchee Ridges lying at the western edge of the Great Valley, a synclinorium of Cambro-Ordovician rocks that stretches from here all of the way to Quebec. I hope you enjoyed the report!

I’ve been manually prepping some fossils I’ve found, nothing too exciting, brachiopods, bryozoans, crinoids stems, etc. I haven’t made a habit of wearing a mask, but I’m starting to doubt my lax habits. I’ve got a sinus headache that won’t quit. Of course there is dolomite dust all around my work area. I guess I’m wondering if it would be better just to make a smallish box with a clear lid and hand/glove holes in the sides. I’m toying with the idea of using my dremel, in which case I would absolutely use a box, but not sure I’m ready to do that. Feel free to let me know if I’ve already killed myself. Thanks!

Newbie here. Discovered this fossil on the shoreline of Bruce Peninsula, Ontario Canada, Lake Huron side in Dolomite rock. Is it Orthocone Ammonoid or Orthocone Nautiloid or something else? I believe these are common finds in the area but this one is much bigger than others I have seen and the creatures shell appears partially fossilized rather than just an impression. Any insight appreciated including possible age. Thank you.

While fossil hunting last year, I collected some shale from between two lenses of Silurian dolomite in Ohio. I have since cooked it down and searched for microfossils, and all I've found (aside from contaminating insect parts) are what appear to me like marbled fragments of bone and what might be . . . denticles? I'm really not sure and would appreciate any suggestions; please see the attached photos. All fossils are about at most 2 or 3 mm in width. Thanks!

What better way to celebrate the end of the year than with a little fossil hunting? And the hunt ended with some spectacular stromatolites; read on! ----- When I got an itch to hit the field last month, I reached out to a quarry in Perrysburg, Ohio to collect fossil and mineralogical samples for donation to academic institutions. The quarry was kind enough to grant me permission to collect on their property for several hours in late December, so when the time came, I suited up and headed out with a trusty assistant. The quarry exposed outcrops of the Lockport and Greenfield Dolomites separated by a thin lens of shale. We were permitted to collect from the outsides of the berm piles surrounding the walls, but I wasn't sure what to expect, as dolomites often exhibit poor fossil preservation, and I had never hunted these units before. Even so, we eagerly hit the berm piles with rock hammers in hand. The quarry wall. The Greenfield Dolomite (red line) sits on top of the Lockport Dolomite (blue arrow), which extends to much deeper than the shelf upon which the photo was taken. The shale horizon between them can be clearly seen as a dark line. Almost immediately, I found a small brachiopod, but then it was several more minutes before we found other fossils. We proceeded to find a variety of reef-building organisms. A small brachiopod (1) and . . . the underside of a Favositid coral (2)? A friend suggested that the larger of these two fossils (3) is a Favositid coral. I'm not sure about the smaller one (4); maybe a bryozoan? This find (5) confused me: it looked like a concretion, seemed to be covered in iron oxide, and had an odd, striped/fluted pattern inside. A friend suggested that it could be slickenslides. It was the only rock that I saw that looked anything like this, and it really stood out against the dolomite. The best finds of the day, however, were undoubtedly the stromatolites. The quarry exhibited them in abundance, and they were readily found throughout the berm piles. The rounded tops of a group of stromatolites. The mottled top of a stromatolite. More layers can be seen just above the left side of the rock hammer. Check out this stromatolite (6)! The coin on it is an American penny. It came from a stromatolite that seemed to be at least 60 or 70 cm in diameter. Not only did we find fossils, however; we also found several crystals, as the dolomites were scattered throughout with crystal-containing vugs. Here's the largest crystal that we found. I haven't tested it with acid, but I suspect that it's calcite. We collected a few other crystals too and even saw some purple ones hiding in a seam in a large boulder. Unfortunately, someone beat me in discovering stromatolites here by many decades, so I didn't make an groundbreaking discoveries, but the trip was nevertheless a wonderful way to round out the year, and all of these samples will end up in academic institutions. May you all have even better fossil hunts in the new year! Cheers, Elasmohunter

OK, I have a question for the learned members of the forum. I finally got some dolomite powder for my blaster (absolutely love it so far!!) and put in a few hours of using it last night, and it raised this question: Do I need to bake my dolomite to dry it before using (or storing)? I have read that dolomite is hydroscopic, and I have noticed this brand new powder has a strong tendency to "bridge" in my media canister. I also had several instances where it seems like a clump of it would exploded on the fossil being prepped. I'm not getting blocked, its not plugging the line or the stylus, so I was wondering if its just trying to stick together into a fluid "clump" as its moving through the line and then exits as a massive hit. I've also noticed how much dolomite loves to stick to EVERYTHING. The inside of my blast box was completely white, even though I have a good air system. This also makes me think it may not drop out in my cyclone as completely as soda, so I may have to add a water trap to keep my vac from cratering. But I digress.... any thoughts on baking the powder? Side question, should I put silica gel in the storage bucket also?

Found by my husband 7/12 near Lander, Wyoming. Sorry for the lack of scale. the whole chunk is about 15cm long. Any leads appreciated! 15 cm long.

Any ideas on this fragment from the Silurian Bisher Fm. Kentucky? Measures 1 cm.

Hey all! Sorry if the information provided isn’t sufficient, but I’m new here. I’m a wildlife biologist and I do a lot of surveying for snakes in rocky areas. A good friend of mine directed me here to help with a fossil ID, as I come across a lot of interesting fossils in the rocks I turn over and the road cuts I search. Attached is a photo of a fossil imprint in a dolomite outcrop. This would be western St Louis County. If more information is required, please don’t hesitate to ask. thanks!

This dolomite stone was discovered near Chasm Creek, central Arizona. It appears to have the fossilized impressions of raindrops splashing into a fine muddy surface. The stone seems to be dolomitic, as HCl causes a low fizz, unlike typical limestone's more energetic fizzing. Most of the "splashes" have the central "rebound" splash seen in my high-speed imagery of water droplets. That central rebound appears to have been broken off over time. Does my assumption that this is a somehow frozen-in-time rain shower make sense?

The fossils in this stone are probably Thamnopora sp., a tabulate coral common in the Verde Valley of Arizona. Normally it appears in dolomite from the late Devonian (Frasnian), This specimen was picked up way outside the normal range, in an ancient riverbed, where rocks generally come from the Martin and Redwall limestone beds to the west. What's weird (to me) is that this stone matrix is impervious to HCl. No reaction at all, as if it's chalcedony, but it doesn't look or feel like chert or any other chalcedony I'm familiar with. Does anyone have an idea what this stone may be and what that might say about its age?

I tried to get some dolomite ready for prepping today, this is first time I've used the dolomite since I got more serious about the quality of my medium, and first time trying pure dolomite. The dolomite I have is raw dolocron from the pottery supply house, I couldn't find any pre-sifted on their website. I used a mortar and pestle, baked the dolomite and sifted through a 120 mesh. Very little powder went through the mesh and what did is still clumping and sticking to surfaces. I don't think it will run through the paasche like this. Here's the mesh after a spoonful of dolomite: And here's what made it through the mesh Is there something I can do to make this workable or do I need to find someplace to buy pre-sifted dolomite?

I'm excited to get into fossil collecting, but before I spend money on gear, I'd like to be able to make an informed decision. The fossils I'd be collecting are from the Silurian age Racine Dolomite. I know that Estwing tools are generally considered the best, but other than that, I am completely unsure as to which hammers and chisels would be most appropriate for breaking these apparently very hard rocks, or even how to go about using them. I know a spot on a friend's property (by the Milwaukee River) where there are a bunch of Silurian rocks piled up, so I don't think access will be a huge problem. Still, info about good sites would be welcome. Thanks.

These tiny fossils I suspect of being Receptaculites, but I'm not at all sure. The patch is about 12x12mm, about the size of a dime. It's on Martin formation dolomite from the Devonian, Verde Valley, Arizona. Other fossils on the same rock include Rugose and Tabulate corals and unidentified Brachiopods. Note the lichens growing in and on the sample. Any ideas?

The attached photo is a group of Thamnopora corals found in the Devonian Martin formation - dolomites of central Arizona's Verde Valley. There is also a group of tabulate corals that I suspect are Syringopora sp.. but some collection notes by others don't show this genus, but they do show Aulopora sp. as found in the same location. See the small worm-like cluster near the center of the image. Can any of you confirm which genus is in the image?

There have been some great reports in the last week of folks hunting the Silurian and I wanted to add a report for my own serendipitous mini-trip from the last weekend. A few months ago, I had noticed a large pile of buff-colored stone dumped next to a retention pond in front of a local retail district. I thought they looked very similar to the Silurian dolomite I have seen and collected from elsewhere in Illinois, so I have been meaning to take a closer look. Last weekend I finally had some errands to run at Target with some free time on my hands, so I wandered over to the pile to check it out. In less than a minute I spotted a friendly face poking out of the corner of one piece of stone- Gravicalymene celebra! An iconic trilobite, and the biggest one I have found, with a cephalon just over 1 inch wide. It looks like it may be complete, although prep can be very difficult as @aek mentioned recently- at a minimum the cephalon appears to all be there. I looked around a little more and found a very poorly preserved cephalopod impression as well as one other rock with some intriguing shapes in it- it will need more prep though to say if it is anything. Since these were dumped next to a parking lot and there are no Silurian dolomite quarries within 60 miles, I can't say for sure what the source is. It seems likely to be the Racine or Joliet Dolomite of northeastern Illinois, though. I will definitely be returning when I have some free time and looking around some more- who knows, they may have used the same stone in other spots around the development!

This partial cephalon was found in rip rap near a quarry that exposes the Silurian Racine Dolomite in Kankakee County, Illinois. I have seen similar examples listed on the auction site, but without IDs. Looking at older publications leads me to think it is Dalmanites, but I'm not positive, and definitely unsure what the species designation would be. Thanks for any help!

Steadly approaching 3 years of collecting from dumped dolomite piles in Milwaukee County has lead to a plethora of "Calymene celebra" molts from Silurian Dolomite of the Racine Formation. Wenlockian. Many hours have been spent with a large sledge hammer breaking out mold of Calymene and other trilobites in similar ways to the Cedarville dolomite in Ohio. The trilobites are almost always complete and are in a noted molting position shown in Weller 1907 An example from my collection and prepped Over the three years we have collected over a hundred complete individuals from the dolomite. About 10 percent of the time we find a Calymene missing its cheeks and in a more flattened preservation. The next most common type of trilobite found is Cheirurus sp. Only 3 complete internal molds have been found of this individual but partials are more common. Likely the species represented here is Cheirurus hydei Found by user evern. As noted this association of trilobites seems to best line up with Hartung Quarry in Milwaukee based on Mikulics Theisis from 1979 on Southeastern Wisconsin Silurian Trilobites. One weird thing is Bumastus being absent from our location, although the chart basically implies only one individual was found. The next trilobites on the list are sparse at best with only a few individuals seen. They are Sphaerexochus, Encrinurus, Dalmanities, Deiphon, Ceratocephala, Acidaspis and Eophacops. The last 4 represented by only 1 specimen each. After finally reading through almost all of Mikulic's dissertation, I am glad to have learned of the location of the stone I have been finding so many trilobites in over the year. Sphaerexochus cephalon Encrinurus Dalmanities Deiphon Eophacops (not mine, Field Museums) Thanks for the read. Hope evern will post his beautiful Dalmanities Cephlon when it is finished prep.

The other day I posted trilobite pics in this ID page thread I just used a beat up drywall saw to cut the section with the trilo out of the slab, then tried to "split" the whacked at the rest of it hoping for more. The siltstone (noncalcareous dolomite maybe?) was so soft it just crumbled. I tried tapping around the edges, which just sort of mashed in, and also tried a chisel, which just took off crumbly flakes (and I wish that was as easy when I try to nap flint). I knew if I found another specimen I'd destroy it trying to get at it, but went for it anyway as a technique-learning excercise. No joy, lots of bits and pieces but no bits and pieces of trilobites Today I collected more of what I THINK is the same material. Before I make a mess of this too, I thought to ask you experts here..... how do you hunt fossils in slabs of really soft crumbly rock? Thanks!

Once again this summer I was able to do a bit of fossil hunting on the edge of a quarry between Shawano, WI and Green Bay. I believe it is Praire du chein, but it could possible be St Peter. At any rate, these three fossils were all found in the same stone, which i believe is dolomite, from approximately 50 feet lower than the surface. (Though not this stone, I found another nearby, that was dolomite with a 2"thick layer of what I would call mudstone, easily broken off in sheets...it contained small as well as small braciapods..a really interesting stone...I had my loop with me, and so looked through the material as i flaked it off the hard dolomite underneath...talk about an intriguing hour. It was really cool to see all the bits and pieces that were in that mudstone. But I didn't have my camera along, so have no photos, only my memory) Getting back to the I,D.s I am curious as to what the deep curled creature might be, and if anyone can tell, or suggest the name of an orthocone for the other two images...They were all on the sides of a boulder easily weighing 1000 pounds. Thanks for any suggestions. Just curious because I hunt in that area alot. BTW...often it is stated that northern wisconsin doesn't have any fossils...that is simply untrue....granted many are ot found on the surface having been scraped away by the glaciers, but there are plenty in the bedrock if one has an opportunity to explore a quarry, as I was able to do..

Hi all, I have been searching through posts in the forum about various types of abrasives, and I can't seem to find a comment anywhere where someone breaks down the pros/cons of the different forms of abrasive and their microns. Of course I realize everyone has their own preferences, I am just confused as to the objective benefits of what looks like the three main types of abrasives: dolomite, aluminum oxide, and just plain baking soda (besides the fact that baking soda is more delicate.) The Paasche Air Eraser comes with 240 micron aluminum oxide, but that seems to be a little extreme for fossil preparation, is there an appropriate time and place in which I could use that? What would be the max (or even a general range) micron of either dolomite or aluminum oxide that one would recommend I use for 1. Green River fish, 2. trilobites, 3. ammonites, or 4. just general fossil clean-up?

I was just wondering if anyone knows the partical size for dolomite as need to order a new tank for the sandstorm abrasion unit. Thanks Matt