Yttrofluorite - Joseph Mine, Rio Arriba County, New Mexico
Contributed by: Chris Clemens
minID: DTE-RR8
Date: May 23rd, 2026
Locality: Joseph mine, Ojo Caliente Mining District, Rio Arriba County, New Mexico, USA (See on Mindat)
Size: 51 x 50 x 75 mm
Weight: 305 g
Description:
Yttrofluorite is a variety of fluorite in which the rare earth element yttrium substitutes for some of the calcium in the fluorite structure. In this specimen, two prominent veins of light grey/white yttrofluorite are encased in a mass of pegmatite with blades of grey muscovite, pink feldspar (var. unknown) and milky quartz. This piece was collected in 2000 at the Joseph Mine, Rio Arriba County, New Mexico.
As shown in the following photographs, the yttrofluorite in this specimen shows a multi-colored, multi-wavelength fluorescent response under UV. Yttrofluorite fluoresces bright pale yellow under shortwave UV (254 nm). Dim red fluorescent feldspar can also be seen under shortwave. Under midwave UV (302 nm) the yttrofluorite shows a pale blue/white, fluorescent response. Under long wave UV (365 nm) the yttrofluorite shows a pale blue, fluorescent response.
Originally posted by Chris Clemens on Nature's Rainbows in 2022.
Summary of luminescence responses:
Yttrofluorite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm Lamp/Mercury) UV light: Blue
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: White
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Yellow