GMS Field Trip May 2023

GMS Field Trip
Pseudodiorite, Microminerals, Slag, and Tour in Tennessee
Tuesday, May 9, 2023

This was our third and final field trip with our new friends from the Chugach Gem and Mineral Society from Anchorage, Alaska. Prior trips to this location have yielded some incredible finds and this trip was no different. We started by collecting pseudodiorite, a rock that occurs as nodules in the graywacke there. It is called pseudodiorite because it resembles diorite, an igneous rock composed of mostly plagioclase (feldspar), biotite (mica), and hornblende, whereas the pseudodiorite is composed of mostly quartz, plagioclase, hornblende, and garnet. Plus, the origin of the pseudodiorite nodules may not have been igneous.

The group went half at a time to tour an area with an old ore bin that is oozing “urban stalactites”, technically called calthemites. We also saw unique iron terrace formations in the creek by the ore bin.

We ended the day on an endless pile of slag. Curious microminerals are hiding inside the slag. I saw at least one clear six-sided crystal and several with very tiny green cubes. Oddly shaped bits of slag with fun shapes are always a treat and this time we found some cute critters – a frog on a dog and a duck in a vug. And, we are convinced that fire-breathing furnace creatures left behind some “slagon skin”.

Once again, we must thank the property owners for welcoming our group to this unusual geological area. They went above and beyond to accommodate our Alaskan friends during a work day. Thank you to all of the field trip attendees for performing perfect car ballets and for being so much fun to collect with. And, of course, thank you to Charles for arranging this trip!

Lori Carter
On behalf of Charles Carter, Field Trip Chair
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