Axinite-(Mg) from Tanzania
Contributed by: Michael Crawford
Date: Jul 17th, 2025
Locality: D-Block Mine, Merelani Hills, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania (See on Mindat)
Size: 6 x 1 x 10 cm
Description:
This is a large crystal of axinite-(Mg) (Ca2MgAl2BSi4O15OH) from the D-Block Mine, Merelani Hills, Tanzania. Formerly known as magnesioaxinite, it was renamed by the International Mineral Association to axinite-(Mg). Part of the axinite group, which also includes axinite-(Mn) and axinite-(Fe), both axinite-(Mg) and axinite-(Mn) can fluoresce.
This specimen shows bright red fluorescence under longwave UV light but appears much dimmer under midwave or shortwave UV light. Axinite-(Mg) emission spectrum features a broad peak at 635 nm and a sharp peak at 687 nm, likely due to manganese and chromium substitution for calcium or magnesium in the structure, though no literature currently confirms these activators.
Summary of luminescence responses:
Axinite-(Mg) (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red