An other example of small but pretty research is the Glava koppargruvan in middle Sweden. It is a hydrothermal Cu-Au deposit with a high amount of tellurides with tellurobismuthite being the dominant Te species. Main ore mineral is bornite, partly converted to digenite and covellite. The wall rock is gneissic with albite-epidote-chlorite alterations. The ore mineralization was mainly bound to a set of more or less parallel quartz veins.
Again, the polished slabs first. The deposit was mined out and what was left was taken by collectors, therefore massive mineralized material is difficult to find now. The material available shows a banded structure with only minor amounts of ore minerals.
Polished slab. Width: 15 cm
Partial scan of the sulfide vein:
Second slab of slightly different host rock. Width: 12 cm
Partial scan of the sulfide rich area:
The polished section with bornite (orange), digenite (light blue) and covellite (deep blue). Nic //, Obj. 20x, air:
The same with Nic. +, Obj. 20x, air. Covellite shows the typical orange anisotropy:
Another part with bornite and covellite. Nic. //, Obj. 20x, air:
Same as above with Nic. +, Obj. 20x, air:
And finally a polished section with the tellurium minerals. Here is a lath of tellurobismuthite in bornite (Nic. //, Obj. 20x, air):
The same with a larger magnification (Nic. //, Obj. 50x, air):
Some of the tellurobismuthite is altered to other Te-minerals, visible in shades of gray. They cannot be identified by ore microscopy, samples will be send to REM-EDX for determination. Nic. //, Obj. 20x, air:
Nic. //, Obj. 50x, air:
Recently I had the luck to have one sample analysed by microprobe EDX to identify some of the tellurides. The sample was prepared from the material of slab one above.
Bornite, Volynskite and Hessite. Nic. //, Obj. 50x, air, 50 µm bar:
Bornite (Bn) with chalcopyrite exsolutions, Volynskite (Vol) and Hessite (Hes). Nic. //, Obj. 125x, oil:
Another spot with the same minerals. Nic. //, Obj. 50x, air, 50 µm bar:
Bornite (Bn), Volynskite (Vol) and Hessite (Hes). Nic. //, Obj. 125x, oil:
Bornite and Hessite. Nic. //, Obj. 50x, air, 50 µm bar:
For further informations on the region these articles might be interesting:
Oen, I.S. and Kieft, C.: Paragenetic relations of Bi-, Ag-, Au-, and other tellurides in bornite veins at Glava, Varmland, Sweden. N Jb Mineralogie Abh.149.(1984).245-266.
Scherbina, A. S.: Die goldreiche Kupferglanz-Bornit-Lagerstätte von Glava im Vermland, Schweden, und ihre geologische Stellung. N Jb Mineralogie Beilage.76.(1940).377-458. (There are quite some mistakes in this one, read it open minded....)