Danburite from Charcas, San Luis Potosi, Mexico
Contributed by: Chris Clemens
Date: Apr 21st, 2026
Locality: Charcas, Charcas Municipality, San Luis Potosí, Mexico (See on Mindat)
Size: 56 x 44 x 66 mm
Description:
Danburite is a calcium borosilicate mineral that is sometimes cut as a gemstone. Like many minerals, when found in its pure form it is not fluorescent, but when trace amounts of certain impurities are present it glows in beautiful colors under UV light. This is an example of a brightly fluorescent danburite specimen from Charcas, San Luis Potosi, Mexico. It consists of a radiating cluster of translucent white danburite crystals to 2.8 cm in length.
This danburite specimen shows its brightest fluorescent response under midwave UV (305nm). Green luminescence is due to the presence of trace amounts of the element uranium, in the form of the uranyl ion (uranium). A similar, but somewhat less bright response is seen under shortwave UV (254nm). A different fluorescent response is seen under longwave UV (365nm), showing a more cream/white color with just a hint of green. The fluorescent activator responsible for the cream/white response is not known.
Originally posted by Chris Clemens on Nature's Rainbows in 2018.
Summary of luminescence responses:
Danburite (Mindat) (RRUFF)
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Green
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green
- Fluorescence under Longwave (365nm LED) UV light: Yellow