A doubly-terminated fluorapatite crystal from the classic locality, the Yates Mine, Otter Lake, Quebec (now closed and the land has been reclaimed). This crystal is complete, with well-defined terminations, good lustre and good green colour at each end.
The crystal also evidences the calcite vein-dike environment in which it formed – the surface has hollows (particularly on the back) and small representative associate minerals including black diopside mixed with titanite. When it grew, this crystal was in a carbonate melt that cooled and crystallized, forming calcite all around the crystal. It is believed that this happened slightly after the fluorapatite crystal formed, and many fluorapatite crystals from Otter Lake and elsewhere in the Grenville Geological Province contain inclusions of calcite and other microminerals that were droplets of the carbonate melt that became trapped as the fluorapatite crystallized.
One notable aspect of Otter Lake fluorapatites – they tended to have well-defined pyramidal terminations and prism faces, unlike many Grenville localities where fluorapatite crystals can be rather rounded and not as well defined.
In excellent condition – the main crystal is great and one of the small fluorapatite side-car crystals does not have terminations. A fine specimen from the Steve Szilard collection.