These two views of the same mineral, idrialite, demonstrate how the complex formation of a mineral can have a strikingly different presentation, depending on conditions. Idrialite, which is sometimes referred to as idrialine, is described as an orthorhombic hydrocarbon mineral. It is also on the soft end of the Mohs scale, with a value of 1.5, according to information from Mindat.org.
This particular specimen was discovered in the prolific cinnabar mine, the Culver-Baer Mine of Sonoma County, California, according to the description posted on the source of this specimen, MRC (Mineralogical Research Co.)’s website, www.minresco.com. Often associated with crystalline to sizable cinnabar, idrialite frequently coats rock matrix or appear as veinlets. It fluoresces bright yellow to golden yellow or yellow-green under short-wave and long-wave UV light.
Photo courtesy MRC, Mineralogical Research Co., www.minresco.com