GMS Field Trip March 2026

GMS Field Trip
Jasper, Agate, Mystery Rocks, Oolitic Jasper in Alabama
Saturday, March 14, 2026

Our first visit to this location was on a Pi Day, i.e., March 14, also expressed using month day as 3-14; with a decimal as 3.14; with math constant symbol as π – basically a day to celebrate math with pastry. It was so much fun we couldn’t resist visiting again on a Pi Day. As on the first trip, members were encouraged to bring pie to share, and WE HAD PIE! From apple to cherry to pecan to pumpkin, and even a chocolate cream pie! We were there to enjoy a day of collecting interesting specimens on massive piles of gravel, and we did. The pies were just the… icing? Anyway, the pie was delicious!

The easiest thing to find there is jasper. Most of the gravel is jasper, mostly brown, mostly plain jasper, but it is not unusual to find black jasper, black and brown together, and some red, pink, or yellow jasper. This time, members found several pieces of pretty jaspers. They polish well, and they tumble well too.

Amongst the brown jaspers, if you look closely, you can find finely banded agate, often referred to as fortification agate. The agate can be hard to see, but a little splash of water brings it out beautifully. Even stained brown from iron, the agate layers are distinct. Members found some pretty agates this time.

The fossils there are a little shy, but members usually find a few nice specimens. A junior found a spectacular piece of fossilized coral, only the second known to have been found there! Hannah found a piece of jasper with two partial shell impressions – one with very well-preserved details. The fossil du jour was petrified wood. Technically, they are not truly petrified wood, but limb casts, because the cell structure was not preserved, just a cast of the outside of the wood. I saw a couple of hand-sized specimens, and several small pieces. While I was working on this report, I noticed a rock that Tim Hellinger slabbed looked like stromatolite, so I sent a picture to Cam Muskelly and he confirmed it! (Stromatolites are formed by sediment trapped in microbial mats.)

My favorite jaspers always come out to play too. They contain tiny, 1 mm to 2 mm spheres called ooliths (oh-uh-liths). Rocks that are composed of ooliths are called oolite (oh-uh-light). Sand, oolite, and other rocks that have ooliths in them are described as oolitic (oh-uh-lit-ick). Ooliths start as individual grains that contain concentric layers of calcium carbonate. Our little ooliths settled into sediment and became cemented together with more calcium carbonate to become rocks. Over time, silica replaced the calcium carbonate and the rocks became oolitic jasper in a process called silicification. You can see individual ooliths as tiny dots in the jasper without magnification, but under magnification, they become much more interesting. You can see cross sections of ooliths, whole ooliths, and voids left by ooliths. Finding oolitic jaspers in the gravel piles is fun! When there is good contrast between the ooliths and the jasper, they are good for lapidary use too.

As fascinating as oolitic jasper is, this location also has some rocks that are equally fascinating, but much more mysterious. Members found some especially nice specimens on this trip. The rocks are usually fairly non-descript at first, but a closer look reveals greenish gray, translucent quartz with layers of light-colored crescent shaped features inside. We have also found crescent shaped marks on the outside of some of the mystery rocks. If you cut one of them open, you will find that the crescents are not throughout the rock. Rather, they are only a few millimeters deep. One thought is that they are a sedimentary pattern that has experienced some metamorphism. Another idea is that the crescents are remnants of percussion marks from other rocks bumping into them during their journey through time and place. The mystery continues to captivate everyone who finds one, and we look forward to learning more about these enigmatic rocks.

Everyone went home with pie in their bellies and goodies in their buckets. This trip would not be possible without the generosity of the property owners and the quarry personnel who always welcome us warmly and keep us safe. We cannot thank them enough for allowing us to explore their giant piles of gravel. Thank you to all of the members who attended. Their perfect adherence to every rule earns us future trips, their pies made the day special, their excitement is contagious, and their graciousness bringing specimens to show me during the trip, and sending me pictures for the trip report afterwards are very much appreciated. Many thanks to Charles for another fun Pi Day in the gravel!

Lori Carter, on behalf of Charles Carter
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