Bustamite from Franklin, New Jersey

Contributed by: Michael Crawford
Date: Nov 21st, 2025
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 6.5 x 9 cm

Description:
A nice specimen of pale pink, massive bustamite (CaMn²⁺(Si₂₆)) from the Franklin Mine, New Jersey. Franklin Mine is the type locality for bustamite. The bustamite fluoresces bright red under longwave UV illumination. It is slightly dimmer under midwave and shortwave light.

The broad red peak shown in the longwave and shortwave emission spectra suggests that manganese is a likely activator for bustamite fluorescence. Manganese is part of bustamite’s composition, but bustamite from Sterling Hill is non-fluorescent, and some bustamite from Franklin is also non-fluorescent. So, there is some impurity or defect in addition to manganese in the bustamite that causes it to fluoresce. It may be more manganese replacing calcium, a co-activator element such as lead, or lattice defects in addition to manganese that activates the red fluorescence. The cause of the broad peak at 450 nm is currently unknown.

The specimen also includes:
Hardystonite (Ca₂Zn[Si₂O₇]),
Clinohedrite (CaZn(SiO₄) · H₂O), and
Willemite Zn₂SiO₄

Hardystonite fluorescence peaks in the ultraviolet with a doublet at 340 nm and 348 nm. The longer wave shoulder of this peak extends into the visible region to produce the observed violet-blue fluorescence. The ultraviolet fluorescence is activated by lead (Pb2+) replacing calcium.

The clinohedrite shortwave emission spectrum has two broad peaks at 573 nm and 601 nm. Manganese is the likely activator of this fluorescence. The doublet peak suggests that manganese replaces two structural positions in the clinohedrite lattice. It might be both calcium and zinc.

The green fluorescence of willemite is also activated by manganese replacing zinc.