Idrialite from the Culver-Baer Mine, 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: 14 x 19 cm
Description:
This is a large specimen of idrialite (C22H14) from the Culver-Baer Mine, West Mayacmas Mining District, Sonoma County, California. The idrialite glows bright green under all wavelengths of UV illumination.
The longwave emission spectrum of the idrialite in this specimen has two sharp peaks at 492 nm and 524 nm characteristic of uranyl activation. The radioactivity of the specimen is slightly elevated at around 80 CPM. There is a second yellow orange, fluorescent mineral. It has no reaction to acid and is resistant to a knife scratch. A tentative ID is opal-AN. Its spectrum has peaks at 493 nm and 527 nm like the idrialite, but the over spectrum is much broader. Organics are also activating fluorescence in the opal-AN.
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