Willemite - Mammoth St. Anthony Mine, Pinal Co. Arizona

Contributed by: Mark Cole
Date: Mar 16th, 2026
Locality: Mammoth-Saint Anthony Mine, St. Anthony deposit, Tiger, Mammoth Mining District, Pinal County, Arizona, USA (See on Mindat)

Description:
Crusts of willemite that fluoresce yellow under LW light and fluoresce pale blue under SW light. Small orange, non-fluorescent wulfenite crystals occur with the willemite.

Originally posted by Mark Cole on Nature's Rainbows in 2015.

Fluorescence under shortwave UV light.

Fluorescence under longwave UV light.

Normal light.

Closeup image of wulfenite crystal.

Summary of luminescence responses:

Willemite (Mindat) (RRUFF)

• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue
• Fluorescence under Longwave (365nm LED) UV light: Yellow