This is a distinctive prehnite from a one-time find in 2006. The first-generation prehnite spheres are quite smooth and have good lustre, and they are overgrown by arcs comprised of coarser prehnite crystals.
These unique specimens are described in the Mineralogical Record article by Rock Currier and Demitrius Pohl “Mineral Collecting in Mali” (May-June 2011, Vol 42:3) and this piece is quite similar to the one from Rock’s collection photographed in Figure 26 of the article. I acquired this specimen from Rock directly and it has been in my collection since.
The prehnite contains prominent dark amphibole inclusions. In the above article, the authors describe how these crystals were originally field-identified as “actinolite”, but the article’s discussion under the amphibole heading confirms that further analysis with Raman spectroscopy indiciates high sodium such that the sampled amphiboles are pargasite (or at least within the pargasite series). The specimens from this prehnite find were not specifically sampled and accordingly this identification assumes some level of amphibole consistency (which, when it comes to amphinboles, is sometimes warranted and sometimes not…)
This specimen is in very good condition – there are a few contacts and rubs, and a couple small incomplete spheres, but minor in the context of piece.
A great piece from an unusual find.