Calcozincite- A Bright Rainbow of Colors from Sterling Hill, New Jersey

Contributed by: Chris Clemens
minID: Q6Y-0HM
Date: Apr 20th, 2026
Locality: Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA (See on Mindat)
Size: 41 x 15 x 92 mm
Weight: 85 g

Description:
This brightly fluorescent specimen of calcozincite was collected during a 2019 night dig at Sterling Hill, New Jersey. Calcozincite is a rock composed of zincite, calcite, willemite, hydrozincite and fibrous minerals such as tremolite, and is found in association with slickensides along fault fractures. This specimen is a light colored, fibrous, asbestiform rock with some black franklinite crystals and red/orange areas of zincite.

Under shortwave UV, this specimen shows a bright rainbow of fluorescent colors. Bright green willemite and red calcite dominate the fluorescent response, with blue, fluorescent accents provided by patches of hydrozincite.
The specimen is also phosphorescent following exposure to shortwave UV. Although the red afterglow of the calcite and the blue of the hydrozincite are short-lived (<2 sec.), the bright green phosphorescence of the willemite persists for 30-60 seconds.

Due to the asbestiform nature of this material, caution should be used when handling to prevent inhalation of the fibers.

Originally posted by Chris Clemens on Nature&apos;s Rainbows in 2020.

Fluorescence under shortwave UV light.

Afterglow after exposure to shortwave UV light.

Normal light.

Summary of luminescence responses:

Calcite (Mindat) (RRUFF)

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

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

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