Lapis Lazuli from the Edwards Mine, St. Lawrence County, New York

Contributed by: Michael Crawford
Date: Aug 18th, 2025
Locality: Edwards Mine (St. Joe Lead), Edwards, St. Lawrence County, New York, USA (See on Mindat)
Size: 4.5 x 7 cm

Description:
This is a lapis lazuli specimen from the Edwards Mine, St. Lawrence County, New York. The lapis lazuli specimen contains blue lazurite (Na7Ca(Al6Si6O24)(SO4)(S3)·H2O) that is non-fluorescent and several minerals that are fluorescent. It has four fluorescent colors under longwave UV illumination. Scapolite (Ca4Al6Si6O24CO3) is yellow, diopside (CaMgSi2O6) is blue, sodalite (Na4(Si3Al3)O12Cl) is orange, and aragonite (CaCO3) on the top of the specimen is blue gray. The aragonite is also phosphorescent. Under midwave UV illumination, the scapolite and sodalite are dimmer, the diopside is brighter, and the aragonite brightest is about the same. The aragonite, sodalite, and scapolite do not fluoresce under shortwave UV illumination. Only the diopside fluoresces bluish white under shortwave illumination.

The fifth image shows the emission spectra of the fluorescent minerals in the specimen. The scapolite and sodalite have vibronic peaks superimposed on a broad peak. The vibronic peaks are caused by a disulfide activator. The diopside and aragonite have broad peaks centered at 450nm. The longwave and shortwave fluorescent response of diopside is the same.

The initial identification of orange, fluorescent mineral in this specimen was sphalerite since it came from a zinc mine. However, the measurement of the emission spectrum clearly shows the vibronic peaks associated with sodalite. The last image shows spectra of orange, fluorescent minerals compared to the orange, fluorescent mineral in the lapis lazuli specimen. The orange fluorescent mineral’s spectrum is very similar to the spectrum of sodalite from Greenland. Both have vibronic peaks at the same wavelengths. The spectra of sphalerite and phlogopite are broad peaks with no vibronic peaks. The maximum peaks of sphalerite and sodalite are similar and as well as their half-widths.