This is a cluster of sharp, lustrous tennantite crystals (up to 2.5 cm on an edge), hosting a few smaller sphalerite crystals (to 0.9 cm). The tennantite crystals on this specimen are robust tetrahedra, with good relief. There is some nice subtle irridescence on this piece. In excellent condition, with minor chipping. There are tetrahedra popping out all over this specimen – nice intergrowth, particularly with small crystals intergrown on the surfaces of the larger ones. Great to have the sphalerites in association – very unusual for Mundo Nuevo. Super piece.
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About these Tennantites
Mundo Nuevo has been best known for its hubnerite, quartz, fluorite and augelite. In recent years there have been occasional excellent finds of tennantite.
These tennantites, mined during 2014-15 specimen recovery work, are part of a find that has now been analyzed quite extensively. Of those (over 40 specimens tested) all were tennantite except one that was a borderline tennantite-tetrahedrite. Accordingly, specimens from this find are now labelled tennantite. I have not had each of these analyzed, given the pervasive tennantite results (and not wanting to add to their prices by incurring unnecessary cost). These tennantites were originally posted on this website labelled “tetrahedrite”, as they were sold to me under that label – they were then removed from the site until the analysis work on the find had been completed.
They are excellent sharp crystals. After the crystals had formed, a late-stage fragmentation and recrystallization event seems to have occurred – the specimens have uneven naturally-fractured surfaces on the back/underside, and these surfaces are recrystallized.