Idrialite from Sonoma County, California
Contributed by: Michael Crawford
Date: Jul 18th, 2025
Locality: Culver-Baer Mine, North Fork Little Sulphur Creek, Cloverdale, West Mayacmas Mining District, Sonoma County, California, USA (See on Mindat)
Size: 5.5 x 8.2 cm
Description:
This is a colorful daylight specimen of white idrialite (C22H14), red cinnabar (HgS), and green pecoraite (Ni3(Si2O5)(OH)4 ). This specimen comes from North Fork Little Sulphur Creek, West Mayacmas Mining District, Sonoma County, California. Only the idrialite is fluorescent. It glows a bright green under all wavelengths of UV illumination.
The idrialite surrounds the green pecoraite grains and separates it from the red cinnabar. The closeup picture shows the rings of green fluorescence around the pecoraite grains.
The emission spectrum of the idrialite in this specimen has two sharp peaks at 494 nm and 523 nm characteristic of uranyl activation. The radioactivity of the specimen is slightly elevated at around 90 CPM.
Summary of luminescence responses:
Idrialite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Green