Willemite - Balmat, New York

Contributed by: Chris Clemens
Date: Apr 30th, 2026
Locality: Balmat, Fowler, St. Lawrence County, New York, USA (See on Mindat)
Size: 46.5 x 28.4 x 66.3 mm
Weight: 130 g

Description:
Light grey, translucent crystals of willemite on and in a light grey matrix, from Balmat, St. Lawrence County, New York. The willemite fluoresces bright green under shortwave UV with bright and lasting green phosphorescence.

Originally posted by Chris Clemens on Nature's Rainbows in 2017.

Fluorescence under shortwave UV light.

Normal light.

Afterglow after exposure to shortwave UV light.

Summary of luminescence responses:

Willemite (Mindat) (RRUFF)

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