GMS     The Georgia Mineral Society, Inc.
4138 Steve Reynolds Boulevard
Norcross, GA 30093-3059

GMS Field Trip

If you have any questions about field trips send email to

GMS Field Trip
Calfkiller Agate & Mississippian Fossils in Tennessee
Friday, November 15, 2019

Collecting in quarries can be hit or miss -- you never know what sort of material is being exposed at any particular time nor what material will have ready access. This time it was a hit! The exposed material was fantastic, plus access to it was super easy. Everyone kept finding outstanding pieces. I was constantly running back and forth trying to get pictures of all the finds.

According to mindat.org, the stratigraphic name of the area is the Monteagle Limestone and its age is Mississippian (358.9 - 323.2 million years old). The place is primarily a limestone quarry, so as one might expect, we were finding fossils, but we were also finding agate nodules and veins. In addition, we observed stylolites, pressure dissolution structures that look like seismograms etched into the limestone. Looking at the strata exposed on the high walls of the quarry, there are at least two striking layers of green material visible. The lower one appears solid and the one higher up in the strata is fairly loose. We found many boulders with flat faces covered with the green material, possibly glauconite, and within the green, many marine fossils including gastropods, some crinoid pieces, and numerous brachiopods. One such boulder had some dark, shiny, fossils with tiny dots. Charles expertly extracted three pieces for me. Kim Cochran and Martha Brown have tentatively identified them as coral, species to be determined.

The star of the day was the agate, often called “Calfkiller” agate. Its curious name comes from a river in Tennessee. It exhibits a range of colors. There are grays from practically colorless to pale blue gray to almost black; browns from watery “root beer” to dark, reddish-brown; and a few bright colors including reds, oranges, and yellows. We found all of these colors. The brown and reddish-brown agates are the most abundant, while reds, yellows, and oranges are a little more elusive. The blue hues, also fairly rare, seem to occur mostly in flat seams, often with flecks and splotches of deep purple fluorite. Diana Poppelreuter found a large seam of blue agate with some parts of the seam coated in fluorite. Anvar Hubbs found a seam of blue with a great deal of purple fluorite mixed in. I found a blue gray nodule with pockets of druzy balls reminiscent of the “grape agate” from Indonesia. Our understanding was that some of the material, particularly the less colorful agate, would fluoresce, so we made sure to collect several pieces. Later, we confirmed almost all of the agates with little or no color in daylight did fluoresce an intense, brilliant green under shortwave light. We also found several pockets of calcite. Some of the calcite fluoresces orange under shortwave and I was told that the calcite is a probable source of the fluorescence in the agate. Everyone found plenty of agate, including the more unusual colors, and we were all ecstatic at the variety we found.

It was an unbelievably good day at this quarry and everyone was grateful for the opportunity to collect there. Many thanks to the powers that be who allow us to visit this quarry (not named here out of respect for the privacy of the property) and all of the employees who made sure we were well-trained and safe. Also, thank you to field trip attendees who generously shared their finds with one another and waited patiently for me to take pictures. And, of course, thanks to Charles Carter for arranging this incredible trip!

Lori Carter
On behalf of Charles Carter, GMS Field Trip Chair
e-mail:
Photo by Lori Carter

quarry
Safety first, all equipment and safety gear verified
Photos by Lori Carter

quarry
quarry
The loose green layer high up on the quarry wall
Photos by Lori Carter

quarry
quarry
The more dense, solid green layer lower in the strata
Photo by Lori Carter

quarry
Typical fossils in the loose green layer (glauconite?) on a boulder
Photo by Lori Carter

quarry
Diana found this gastropod weathering out
Photo by Lori Carter

quarry
Some of the fossils Diana extracted
Photo by Lori Carter

quarry
Close-up of Diana's tiny gastropod in matrix
Photos by Lori Carter

quarry
quarry
Unidentified tiny fossils in matrix that we were unable to extract
Tip of glove finger lower right for scale in top picture
Close-up in bottom picture
Photos by Lori Carter

quarry
Boulder that had the coral fossils (glove for scale)
quarry
quarry
One set in situ (tip of glove top left for scale)
quarry
quarry
Larger of the two with close-up
quarry
quarry
Smaller of the two with close-up
quarry
quarry
quarry
Another specimen in-situ followed by close-ups
Photo by Lori Carter

quarry
Calfkiller agate with a nice "eye" pattern
Photos by Lori Carter

quarry
quarry
Calfkiller agate with brown, red, yellow, and orange
Photos by Lori Carter

quarry
quarry
Ivy and his favorite big agate
Photo by Lori Carter

quarry
Juergen and his yard rock
Photo by Lori Carter

quarry
Charles on a quest for his own prize
Photos by Lori Carter

quarry
quarry
quarry
quarry
Calcite
Photo by Lori Carter

quarry
quarry
Tiny sedimentary structure with close-up
Photos by Lori Carter

quarry
quarry
quarry
Deep purple fluorite
Photos by Lori Carter

quarry
quarry
Diana working on a blue agate seam
Photos by Lori Carter

quarry
quarry
Anvar's blue agate with purple fluorite
Photos by Lori Carter

quarry
quarry
quarry
Blue seam agate with purple fluorite in limestine matrix
Photos by Lori Carter

quarry
quarry
quarry
quarry
quarry
Gray, almost colorless agate that fluoresces under shortwave light
Photos by Lori Carter

quarry
quarry
Agate under visible spectrum and shortwave
Photos by Lori Carter

quarry
quarry
quarry
Blue agate nodule with close-up of druzy spheres
Photo by Lori Carter

quarry
quarry
More eye candy
Photo by Lori Carter

quarry
quarry
This one has color under both lights

Click below for field trip policies

policies
Copyright © Georgia Mineral Society, Inc.