GMS Field Trip

GMS Field Trip
Epidote and Grossular Garnet Xenoliths in Granite,
Pyrite, and Scolecite in Georgia
Sunday, November 4, 2018

In November, GMS members visited a quarry that contains some fascinating geology. The area we visited has many xenoliths. The word “xenolith” is from the Greek “xenos” meaning foreign, and the Greek “lithos”, meaning stone, so it is basically one type of rock trapped in another type of rock. This usually occurs when magma rises through the earth’s crust and bits of country rock fall into the magma. Chunks that maintain their composition and are not completely dispersed into the magma are called xenoliths. At this quarry, we saw many examples of metamorphic xenoliths in granite. The xenoliths contain epidote and reddish orange grossular garnet. We also collected some pink specimens, probably feldspar or calcite, as well as some pyrite. David Bruce found a spray of clear, thin crystals. Last year, Daniel Miller found a similar specimen and it was confirmed to be scolecite. A last minute find by Diana Poppelreuter had Juergen and Charles frantically trying to extract a chunk from a boulder as we were leaving, but alas, the specimen, possibly aquamarine, had to be left behind in its rocky abode. On the way out though, thanks to quarry personnel, Charles and I managed to retrieve a small boulder with good examples of xenoliths to put in front of the GMS building. It was a great day of collecting and everyone I talked to had a lot of fun.

Many thanks to the quarry personnel who patiently answered all of our questions and made sure we were always safe. And thanks to Charles for arranging this excellent geology trip.

Lori Carter
On behalf of Charles Carter, GMS Field Trip Chair
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