Greenockite from Pennsylvania
Contributed by: Michael Crawford
Date: Jun 28th, 2025
Locality: Friedensville, Upper Saucon Township, Lehigh County, Pennsylvania, USA (See on Mindat)
Size: 2 x 3.5 cm
Description:
This is an earthy yellow coating of greenockite (CdS) that was deposited on a fracture surface. The specimen comes from Friedensville, Lehigh County, Pennsylvania. Greenockite is the hexagonal crystalline form of cadmium sulfide. Hawleyite is a polymorph of the same chemical formula but forms isometric crystals. Only greenockite is reported from Friedensville.
Greenockite fluoresces red under longwave and midwave UV illumination. Hawleyite fluoresces orange under longwave illumination. The greenockite longwave emission spectrum has a broad peak in the visible red and near infrared with a maximum at 706 nm. There is another small peak at 518 nm. I could not find any information on what activates the fluorescence in greenockite.
Summary of luminescence responses:
Greenockite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Midwave (305nm LED) UV light: Red