Charoite, Microcline, and Steacyite from Russia
Contributed by: Michael Crawford
Date: Jun 24th, 2025
Locality: Murunskii Massif, Chara and Tokko Rivers Confluence, Aldan Shield, Russia (See on Mindat)
Size: 9 x 14.5 cm
Description:
This is a polished slab of purple charoite ((K,Sr)15-16(Ca,Na)32[Si6O11(O,OH)6]2[Si12O18(O,OH)12]2[Si17O25(O,OH)18]2(OH,F)4 · ~3H2O), black aegirine, white microcline, light brown tinkasite, and steacyite (K0.3(Na,Ca)2ThSi8O20) from the Murunskii Massif, Chara and Tokko Rivers confluence, Aldan Shield, Russia. The microcline fluoresces red under all wavelengths of UV light. XRD analysis identified the microcline in this slab. Ferric iron is the likely activator of the red fluorescence.
According to mindat.org, the scattered grains of a green fluorescent mineral in the slab are likely steacyite. Steacyite is a thorium-bearing mineral, where uranium has replaced some of the thorium, causing green fluorescence under all wavelengths of UV light. The longwave emission spectrum contains two sharp peaks at 511 nm and 528 nm, indicative of vibronic uranyl activation.
The last three pictures show a close-up of green fluorescent steacyite grains and red fluorescing microcline in another charoite specimen. The largest steacyite grain in the picture is 2mm long.
Summary of luminescence responses:
Microcline
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Midwave (305nm LED) UV light: Red
- Fluorescence under Shortwave (255nm LED) UV light: Red
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Green