THROWING SNOW & WONDERING ABOUT DJURLEITE

 

Wisconsin life in the snow and cold lane. Looking forward to tomorrow (Feb. 17) with a robust high of 0 (zero) F and a low of minus 17 F. But I do have many friends!

During the long winter months in the Northland I enjoy sorting through the many Perky Boxes that have accumulated during my mineral wandering. The other day, as I was contemplating the fact we have gained 3 hours and 30 minutes of daylight since the December Winter Solstice, I pulled out a specimen with several small notes stuffed in, or tapped to, the box. The specimen was djurleite, a copper sulfide (Cu₃₁S₁₆), with a confusing collecting history; hence, my stuffed notes from a past deciphering episode.

Djurleite is a member of the Chalcocite Group, all members being copper sulfides not known for their beauty. These sulfides are typically black in color with a luster ranging from metallic to dull unless a light hits them and they appear in various shades of gray. All are opaque, and quite soft at about 2.5—3.0 (Mohs). One essentially needs an XRD to make a final identification. A statement from Pósfai and Buseck (1964) seems way above my paygrade: “chalcocite easily converts to djurleite under electron beam through the rearrangement of Cu atoms.” That publication appeared at the time in my undergraduate life when I was enrolled in a Mineralogy and suffering through crystallography. Electron beams rearranging atoms was nowhere in my vocabulary. Another fascinating item about djurleite is that that the mineral was named for Dr. Seved Djurle, a professor of Chemistry at the University o Uppsala in Sweden. Dr. Djurle was not a rockhound nor geologist but a chemist who synthesized djurleite before the mineral was discovered. That tidbit seems quite impressive to me!

So, back to the collecting history of my specimen.  My purchase was made four years ago in Tucson from Michael Shannon and was an Ex David Shannon.  The collecting locality on the ID card stated Djurleite, Reutanieme, Lapland, Sweden. A small cryptic note simply said “XRD.” So off to Mindat where Reutanieme was not listed as a collecting locality for any mineral nor was djurleite listed as a mineral found in Swedish Lapland. What’s an ole plugger like me to do? Well, for starters, hit the Internet! And guess what I found? From 2021 a question in the MinDat Discussion Group about Djurleite: “I obtained this djurleite in a fuschite schist labeled as coming from an outcrop near the town of Reutanieme, Lappland, Sweden and was collected by the late great Ingemar Johansson in the 1990s according to the accompanying David Shannon Minerals label. I can find no reference to any such town in the Lapland areas of Sweden or Finland for that matter. Any help is appreciated.” The best answer provided by Andŕe Heyninck was this: “In 1991 I exchanged several Collecting information for a specimen in the collection of minerals with Ingemar Johanson, including djurleite from the Naesmark site, Norway. See photo. I hope this will help you further.”

Label of Djurleite in the collection of  Andŕe Heyninck. From MinDat Discussion Group (accessed February 2025).  

Therefore, off I went from Sweden hopping over to Norway and the Naesmark Mine. The Naesmark is part of a collection of copper mines generally assigned to the Amdals Verk Mine/District in Telemark. I cannot locate much information about the mines and mining activity except that MinDat (February 2025) lists 417 minerals known from Telemark and djurleite is rarely noted. This scarcity may be due to its relationship with chalcocite and digenite as perhaps all were mixed together and tossed into the processing plant. After all, who would want to collect pretty ugly black specimens?

Above photomicrographs with width FOV ~6 mm. Some show very shiny metallic luster while others point to a dull metallic luster. All are associated with quartz.

So, what am I supposed to do about collecting locality for my specimens? I could just leave it alone with the Reutaneeme, Lapland, Sweden notation, or I could switch the locality to the Naesmark, Telemark, Norway notation. Since my specimen looks “very related” to my specimen photo on MinDat I will go with the Norway collecting site. However, it could be from Sweden (doubtful) or one of several mines in Norway (likely).

That is about my total knowledge of the copper sulfide djurleite. It seems somewhat uncommon in copper mining areas when one examines total “numbers” of specimens. However, my uneducated thought is that djurleite is often mistaken for common chacosite.in the enriched supergene copper deposits.

REFERENCES CITED

Pósfai, M. and Buseck, P. R., 1994, Djurleite, digenite, and chalcocite: Intergrowths and transformations: American Mineralogist, No. 79.

What good is the warmth of summer, without the cold of winter to give it sweetness.

John Steinbeck in Travels with Charley in search of America.