Fluorite and Willemite from the Red Cloud Mine, La Paz County, Arizona

Contributed by: Chris Clemens
minID: JLG-506
Date: Apr 21st, 2026
Locality: Red Cloud Mine, Silver Mining District, La Paz County, Arizona, USA (See on Mindat)
Size: 58 x 43 x 73 cm
Weight: 113 g

Description:
Located in the Trigo Mountains of La Paz County, Arizona, the Red Cloud mine is a location famous for producing some of the best wulfenite specimens in the world. Not generally known, however, the Red Cloud mine is also a prolific source of beautiful fluorescent minerals. This example from the Red Cloud mine features a very pleasing color combination of intense blue, fluorescent fluorite, pale blue/green willemite and minor red calcite. As seen in the following photographs, the willemite only responds under shortwave UV (254nm) and the fluorite shows its brightest response under longwave (365nm).

This Red Cloud mine specimen displays best under fullwave UV (SW+MW+LW). The fluorite shows an intense blue/purple response, the willemite pale blue/green and the minor calcite fluoresces red. The willemite fluoresces brightly and the fluorite is somewhat diminished under shortwave UV compared to the fullwave image. After the shortwave lamp is turned off, the willemite continues to phosphoresce. The fluorite also shows very brief, dim phosphorescence.

Under longwave UV the fluorite shows a bright and intense blue/purple, fluorescent response, and the other minerals are not reactive. Due to limitations of the camera's image sensor, it was not possible to capture the true brightness of the long wave response as the eye sees it. When viewed in-person, the longwave response of this specimen appears much brighter.

Originally posted by Chris Clemens on Nature's Rainbows in 2018.