Idrialite, a Rare Organic Fluorescent Mineral

Contributed by: Chris Clemens
Date: May 24th, 2026
Locality: Culver-Baer Mine, North Fork Little Sulphur Creek, Cloverdale, West Mayacmas Mining District, Sonoma County, California, USA (See on Mindat)
Size: 56 x 46 x 81 mm
Weight: 200 g

Description:
The vast majority of fluorescent minerals are composed of inorganic materials. There are a few exceptions, however. Idrialite is one such exception. Idrialite is a rare, organic, hydrocarbon-based mineral having the chemical formula C₂₂H₁₄, and it shows a beautiful fluorescent response under UV ranging from green to orange. This specimen provides an excellent example of this rare organic fluorescent mineral. It was collected from the Culver-Baer mercury mine, Cloverdale, Sonoma County, California. This rock consists of a tan/yellow matrix with blue/grey quartz veins and druse. Minor crystals of purple/red cinnabar are also present. The idrialite appears to be included in the quartz.

Originally posted by Chris Clemens on Nature's Rainbows in 2021.

Fluorescence under shortwave UV light.

Normal light.

Summary of luminescence responses:

Idrialite (Mindat) (RRUFF)

• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green