Ruby from Tanzania
Contributed by: Michael Crawford
Date: Jul 22nd, 2025
Locality: Tanzania (See on Mindat)
Size: 3.3 x 7.5 cm
Description:
A corundum var. ruby (Al2O3) hexagonal crystal from Tanzania. The crystal has bright red fluorescence under longwave UV illumination and it is less intense under midwave and shortwave light. The red color and red fluorescence are due to chromium (Cr3+) replacing alumimum. The emission spectrum of ruby is very distinctive. It has a very sharp, bright peak at 692 nm. There are two much smaller peaks on each side of the big peak. These peaks are at 659 nm , 669 nm, 706 nm, and 713 nm.
Summary of luminescence responses:
Corundum var. Ruby (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Midwave (305nm LED) UV light: Red
- Fluorescence under Shortwave (255nm LED) UV light: Red