Amazonite and Albite from Franklin, New Jersey
Contributed by: Michael Crawford
Date: Jul 28th, 2025
Locality: Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 9 x 10
Description:
Blue-green amazonite and (Na(AlSi3O8)) albite from Franklin, New Jersey. Amazonite is a variety of microcline (K(AlSi3O8)). The blue-green color of microcline has been attributed to elevated lead content, but ferrous iron (Fe2+) may also contribute to the color. Microcline and albite are feldspars. They are endmembers of a solid solution series between potassium-rich feldspar (microcline) and sodium-rich feldspar (albite). This specimen contains both types of these feldspars.
The specimen has a greenish gray fluorescence under shortwave UV illumination. It is non-fluorescent under longwave and midwave UV light. The shortwave emission spectrum has a broad peak with a maximum at 464 nm. The activator for this fluorescence is currently unknown. This emission dominates the fluorescence we see.
The spectrum also has two smaller peaks in the red and near infrared at 686 nm and 722 nm. Shortwave emission spectra of microcline specimens have a single peak around 680-690 nm that is activated by ferric iron (Fe3+). Albite shortwave emission typically peaks around 720 nm. This albite emission is also activated by ferric iron (Fe3+). The double peaks in this specimen indicate that microcline and albite are both present.
The color infrared image shows areas in the specimen where the composition of the feldspar is dominated by microcline or by albite. Microcline is light blue and albite is red.
Summary of luminescence responses:
Amazonite (Mindat) (RRUFF)
- Fluorescence under Shortwave (255nm LED) UV light: White