Kyanite from Brazil
Contributed by: Michael Crawford
Date: Aug 20th, 2025
Locality: Minas Gerais, Brazil (See on Mindat)
Size: 6 x 8.5 cm
Description:
Blue kyanite (Al2(SiO4)O) crystals from Minas Gerais, Brazil. Most blue kyanite from Brazil is non-fluorescent. This specimen fluoresces bright red under longwave UV illumination. It is non-fluorescent in midwave and shortwave light.
The emission spectrum has two large very sharp peaks at 688 nm and 704 nm. There are two smaller peaks at 721 nm and 732 nm. These sharp peaks are superimposed on a broader peak. Most of this broader peak is in the near infrared with a maximum around 720 nm. The fluorescence is activated by chromium (Cr3+) replacing aluminum (Al3+). According to fluomin.org, there are three different aluminum sites in kyanite where chromium can substitute that are responsible for the sharp and broad peaks in the emission spectrum.
Summary of luminescence responses:
Kyanite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red