Brilliant Green Fluorescent Willemite from the Sterling Mine

Contributed by: Chris Clemens
Date: Apr 23rd, 2026
Locality: Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA (See on Mindat)
Size: 41.4 x 19.5 x 45.4 mm
Weight: 80 g

Description:
A red/brown, somewhat rhombohedral, piece of nearly pure willemite, with minor calcite. This red variety of willemite contains manganese and is known as Troostite. Under shortwave UV the willemite fluoresces very bright green with lasting phosphorescence, and two small areas of calcite show a typical red response. The specimen shows a similar, but less bright, response under longwave UV.

Originally posted by Chris Clemens on Nature's Rainbows in 2016.

Fluorescence under shortwave UV light.

Afterglow after exposure to shortwave UV light.

Fluorescence under longwave UV light.

Normal light.

Summary of luminescence responses:

Willemite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Green
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green
• Afterglow after exposure to Shortwave (254nm Lamp/Mercury) UV light: Green