Arfvedsonite on Microcline
Posted by: macadmin on 05.14.2020 | Filed under:

Arfvedsonite on Microcline

Specimen # 101940
Mineral: Arfvedsonite on Microcline
Location: Arfvedsonite on Microcline, Mount Malosa, Zomba District, Malawi
Size: 6.8 x 4.7 x 4.0 cm


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.

Additional information

Dimensions 40 × 68 × 47 cm