Johnbaumite, Svabite and Calcite from the Jakobsberg Mine, Sweden
Contributed by: Michael Crawford
Date: Jul 26th, 2025
Locality: Jakobsberg Mine, Jakobsberg ore field, Nordmark mining district, Filipstad, Värmland County, Sweden (See on Mindat)
Size: 9 x 12 cm
Description:
A specimen of johnbaumite (Ca5(AsO4)3(OH)), svabite (Ca5(AsO4)3F), and calcite (CaCO3) from the Jakobsberg Mine, Nordmark Mining District, Filipstad, Varmland County, Sweden. The Jakobsberg Mine is the type locality of svabite. Johnbaumite and svabite are arsenic apatites.
The first image shows the specimen illuminated by shortwave (255nm LED) light. The johnbaumite fluoresces violet, the svabite fluoresces orange, and the calcite fluoresces red.
The shortwave emission spectra show of the shortwave fluorescence of the three minerals. The fluorescence of the minerals is significantly brighter in the ultraviolet region compared to the visible fluorescence. The red visible fluorescence of the calcite is caused by a manganese activator. The ultraviolet fluorescence of the calcite has a peak around 310 nm and is activated by lead.
The spectra of the johnbaumite and svabite are similar. Both have a broad peak in the visible region with a maximum around 600 nm. This visible peak may be caused by a manganese activator. Both minerals have another fluorescent peak in the ultraviolet region with three maxima at 350 nm, 370 nm and 385 nm. This ultraviolet fluorescence is likely caused by cerium. The intensity difference of the ultraviolet fluorescence compared to the visible fluorescence is considerably greater for the johnbaumite. The shoulder of the johnbaumite’s ultraviolet fluorescent peak extends into the visible violet and blue. The intensity of the violet fluorescence from this shoulder overwhelms the orange fluorescence and makes the johnbaumite appear violet. The corresponding of the violet fluorescence of the svabite is considerably less intense and the orange fluorescence dominates.
The last picture shows a false color image of the ultraviolet fluorescence. Three narrow bandwidth filters centered at 310 nm, 350 nm, and 394 nm were used to capture images at each of these filter wavelengths. The filters are shown on the spectral plots. The 310 nm image was assigned to blue, the 350 nm image was assigned to green, and the 394 nm image was assigned to red to create the false color image. Calcite is light blue and the johnbaumite and svabite are yellow in the false color image. The johnbaumite and svabite are easily differentiated in this false color image. The area of svabite has a slightly darker color.
Summary of luminescence responses:
Svabite (Mindat) (RRUFF)
- Fluorescence under Shortwave (255nm LED) UV light: Orange
- Fluorescence under Shortwave (255nm LED) UV light: Violet
- Fluorescence under Shortwave (255nm LED) UV light: Red