Fluorapatite and Calcite from the Liscombe Deposit, Ontario, Canada
Contributed by: Michael Crawford
Date: Jul 26th, 2025
Locality: Liscombe Deposit, Cardiff Township, Highlands East Township, Haliburton County, Ontario, Canada (See on Mindat)
Size: 8 x 9 cm
Description:
Gemmy green fluorapatite (Ca5(PO4)3F) crystals in a pink calcite matrix. The specimen is from the Liscombe Deposit, Cardiff Township, Haliburton County, Ontario, Canada. An interesting feature of this specimen is the nearly parallel orientation of the fluorapatite crystals in the calcite matrix. A possible explanation is that the fluorapatite crystals formed first and became aligned in a flowing hydrothermal fluid. At some point, the temperature, pressure, or other condition changed to cause the calcite to precipitate and preserve the crystal orientation.
The fluorapatite and calcite fluoresce brightly under midwave UV illumination. The fluorapatite glows light blue and the calcite is orange-red. The fluorescence is dimmer under shortwave UV illumination and the color of the fluorapatite fluorescence changes to blue-grey. The orange-red calcite fluorescence is activated by manganese. The light blue fluorapatite fluorescence is activated by rare earth elements.
Both minerals also fluoresce in the ultraviolet region under shortwave UV light. The fluorapatite ultraviolet fluorescence has a single peak at 342 nm. The calcite UV fluorescence has a primary peak at 340 nm and a secondary peak at 363 nm. The ultraviolet fluorescence in both minerals is likely activated by Ce3+.
The last picture shows the ultraviolet fluorescence. The picture is composed of three narrow bandpass filter images. The filters are centered at 310 nm, 350 nm and 375 nm. The fluorapatite is green in the false color image of ultraviolet fluorescence and the calcite is yellow green. The two minerals have the same brightness in the 350 nm image. The calcite is brighter in the 375 nm image because of the secondary fluorescent peak at 363 nm. The 350 nm and 375nm images are assigned to green and red respectively. Green and red combine to form the yellow calcite response shown in the ultraviolet image.
There is very weak longwave fluorescence. The fluorapatite has a faint brown LW fluorescence.
Summary of luminescence responses:
Fluorapatite (Mindat) (RRUFF)
- Fluorescence under Midwave (305nm LED) UV light: Blue
- Fluorescence under Shortwave (255nm LED) UV light: Blue
- Fluorescence under Midwave (305nm LED) UV light: Red