Calcite, Willemite, Franklinite and Zincite: A Sterling Hill, New Jersey Classic

Contributed by: Chris Clemens
Date: May 2nd, 2026
Locality: Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA (See on Mindat)
Size: 8 x 6.1 x 13 cm
Weight: 761 g

Description:
This is a classic, bright fluorescent specimen from the famous Sterling Mine in Sterling Hill, Ogdensburg, New Jersey. This piece contains the three primary zinc ore minerals willemite, franklinite and zincite, that put the historic Franklin/Sterling Hill zinc mines on the map. This specimen also contains abundant calcite, which back in the days of zinc mining would have been considered an undesirable gangue mineral. Under shortwave UV, the willemite fluoresces bright green with phosphorescence, and the calcite shows bright orange/red fluorescence, typical for this material. The calcite also shows a phenomenon known as brief intense phosphorescence, or "BIP", meaning that for a brief moment immediately after the shortwave lamp is turned off, it displays a very short-lived, but bright (intense) phosphorescent response or flash. Under longwave UV the calcite shows a dim to moderate magenta response and the willemite fluoresces dim green.

Originally posted by Chris Clemens on Nature's Rainbows in 2018.