Calcite Geode from Lewis County, Missouri
Contributed by: Mark Cole
Date: Apr 4th, 2026
Locality: Lewis County, Missouri, USA (See on Mindat)
Description:
Some friends stopped by returning from their visit to the annual Keokuk Geodefest in the Illinois area. They collected a massive number of quartz geodes, much like the ones I find here in middle Tennessee - few have any significant fluorescence. But they also "silver-picked" a couple of very nice geodes with calcite interiors - nicely fluorescent. This specimen has white calcite crystals sticking out of a bed of non-fluorescent dark brown calcite. The dogtooth calcite is a pretty violet, strongest under midwave UV light while the calcite encircling is a beautiful yellow/tan. The quartz exterior has a mottled white fluorescence.
NOTE: Per direct communication from the person who found these geodes: "....there is no fluorite in these geodes (from your article) I\'ve had analysis done on these specimens as well as some simple acid tests. I\'ve collected and opened more than 80,000 specimens and understand the minerals in this area very well. " - so, not fluorite, but still very pretty.
The locality was given as Lewis County - specific information kept secret.
Originally posted by Mark Cole on Nature's Rainbows in 2016.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Orange
- Fluorescence under Longwave (365nm LED) UV light: Orange