Emerald from the Muzo Mine, Colombia
Contributed by: Michael Crawford
Date: Aug 29th, 2025
Locality: Muzo Mine, Muzo Municipality, Western Boyacá Province, Boyacá Department, Colombia (See on Mindat)
Size: 4 x 6 cm
Description:
Green crystals of emerald from the Muzo Mine, Colombia. Emerald is a variety of beryl (Be3Al2(Si6O18)). The emerald crystals occur in a vein of calcite and quartz. The vein cut black shale that is exposed on the bottom of the specimen. Trace amounts of chromium, vanadium, and iron are responsible for the green color in daylight. Chromium (Cr3+) and ferric iron (Fe3+) can also cause it to fluoresce under longwave UV light. The emerald is non-fluorescence under midwave and shortwave light. Many emeralds do not fluoresce, and the typical red fluorescence is modest.
The longwave emission spectrum of this Colombian emerald differs from other spectra of red fluorescent emeralds from Colombia. Both spectra have a sharp peak at 684 nm caused by chromium. The sharp peak occurs on the shoulder of a much broader peak with a maximum in the near infrared. The difference between the two Muzo emeralds is the broad peak in the near infrared. One emerald has an asymmetric peak with a maximum at 713 nm. The Muzo emerald in this post has a symmetrical peak with a maximum at 731 nm. This emerald peak shifts to 726 nm in the 405 nm laser spectrum. The difference in the two spectra suggest smaller amounts of chromium in the emerald with the 731 nm peak, and perhaps ferric iron contributes more to the activation of the red fluorescence in this specimen.
The last two images show the infrared fluorescence of the emerald. The emission spectra show that the infrared fluorescence is brighter than the visible fluorescence.
Summary of luminescence responses:
Beryl var. Emerald (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red