Mexican Geode with Fluorescent Drusy Chalcedony and Calcite with Phantoms
Contributed by: FMS Admin
Date: Feb 27th, 2026
Locality: Mexico, Mexico (See on Mindat)
Size: 4.5 x 1.5 x 6 inches
Weight: 1.5 lb
Description:
This was a fortuitous find at a local mineral show. Just like with oysters, one never knows what one will find in a geode. In addition to the green fluorescing chalcedony [likely uranyl activated] it has calcite [fluoresces pink red] and aragonite [fluoresces faint blue]. The calcite fluorescence is caused by phantoms while the aragonite also phosphoresces. No pictures of the phosphorescence as it was pale and brief. No real LW fluorescence.
Shortwave pictures were taken at ISO-100, f/11 for 2.5 seconds.
Originally posted by John Rofrano on Nature's Rainbows.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green