Emerald from the Muzo Mine, Colombia
Contributed by: Michael Crawford
Date: Aug 28th, 2025
Locality: Muzo Mine, Muzo Municipality, Western Boyacá Province, Boyacá Department, Colombia (See on Mindat)
Size: 1.5 x 3.5 cm
Description:
A small hexagonal crystal of emerald in a matrix of calcite from the Muzo Mine, Colombia. Emerald is a variety of beryl (Be3Al2(Si6O18)). 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. 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 has a sharp peak at 684 nm. The peak is at 683 nm in the 405 nm laser spectrum. Chromium (Cr3+) activates the red fluorescence that causes this sharp peak. The sharp peak occurs on the shoulder of a much broader peak with a maximum at 714 nm in the near infrared. The maximum is asymmetric due to a second peak around 727 nm. Chromium is likely responsible for the peak of 714 nm. The 727 nm peak may be caused by either chromium or ferric iron.
The second plot compares emission spectra of red fluorescent emeralds excited by a 405 nm laser source. All spectra have the sharp peak at 683 nm. The broad peaks in the near infrared region are different. Three spectra have peaks with maximum at 713 nm and a second peak around 727 nm. The other two spectra have single peaks with maximum at 727 nm.
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