Margarosanite from Franklin, New Jersey

Contributed by: Michael Crawford
Date: Nov 28th, 2025
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 9 x 10 cm

Description:
Margarosanite (Ca₂PbSi₃O₉) is a rare lead-silicate mineral and the Franklin Mine is its type locality. Margarosanite is one of the minerals associated with the Parker Shaft assemblage. It is a metamorphic mineral formed during a hydrothermal event that altered the original Franklin zinc deposit.

Margarosanite is a highly sought after mineral because of its bright violet blue fluorescence under shortwave UV illumination. This specimen also contains green, fluorescent willemite (Zn₂SiO₄) and pectolite (NaCa₂Si₃O₈(OH)) that fluoresces orange.

The shortwave emission spectrum of margarosanite has three peaks. One peak is in the ultraviolet region with a maximum at 320 nm. This peak is activated by lead (Pb2+). Lead also activates the violet blue fluorescence. Its emission maximum is a doublet with peaks at 433 nm and 446 nm. The third peak in the visible red is the least intense of the three peaks. Its maximum is at 618 nm. It is activated by manganese.

The red fluorescence caused by manganese activation becomes dominant under midwave illumination. The midwave emission spectrum of the red fluorescence has a maximum at 614 nm. There is no longwave fluorescence.

Fluorescence under shortwave UV light.

Fluorescence under midwave UV light.

Normal light.

Incorrect labels. Corrected in the next image

Emission Spectra

Summary of luminescence responses:

Margarosanite (Mindat) (RRUFF)

• Fluorescence under Shortwave (255nm LED) UV light: Blue
• Fluorescence under Midwave (305nm LED) UV light: Red

• Fluorescence under Shortwave (255nm LED) UV light: Green

• Fluorescence under Shortwave (255nm LED) UV light: Orange