Sharp arfvedsonite crystals adorn the top of a block of microcline. These are great crystals of arfvedsonite – the prism faces are highly lustrous, while the terminations are matte. To me, the coolest aspect of this piece is that the prism faces have a fascinating pattern on them, where there is a shape that is slightly less lustrous, surrounded by glassy-lustre. Hard to know if this is due to selective etching.
I should add that one other possible explanation of the pattern on the prism faces could be a selective deposition of a late sodium-rich phase. We have seen a comparable phenomenon of a late sodic phase in the crystallization of amphiboles and feldspars here in Ontario. This possibility is supported by the presence of a selective albite overgrowth on certain faces of microcline – hard to make out on this specimen (though present), and prominent on specimen 101941.
In excellent condition – the arfvedsonite crystals are super, with a couple of minor chips. Some incomplete microclines and an incomplete arfvedsonite at the periphery. The microcline fluoresces deep pink-red under shortwave ultraviolet light.
This is a very fine specimen of arfvedsonite.