The Schöne Aussicht mine near Burbach in Siegerland:
Location of many rare minerals
Text by: Johannes Markus Henrich, Kirchen, Matthias Reinhardt, Drolshagen and Günter Frenz, Cologne.
The heap of the upper gallery of the pit Schöne Aussicht. Photo: Markus Henrich.
Somewhat away from the well-known Peterszeche, Victorsfeld (Bleiberg) and Green Hope pits in Buchhellertal, on Burgberg (591 m above sea level) near Burbach in southern Siegerland, there is the Schöne Aussicht mine. It is an interesting site for a large number of very rare and sometimes very beautiful minerals that we would like to introduce in this article.
The Schöne Aussicht mine built on a lead, zinc and copper ore deposit in the eastern extension of the deposit of the green hope and star of hope pits. The vein zone with a few small deposits extends further into the Gambach valley south of Burbach. In contrast to the mines in Buchhellertal, little is known about mining here. In the mountain area description by HUNDT et al. (1887) it is written that the Schöne Aussicht mine had not gotten beyond research work until then. Two short day shafts and two tunnels, which presumably date from the second half of the 19th century, developed and examined the deposit together with a blind shaft and dies at different depths. White lead ore (cerussite) and lead luster (galena) were found in "narrow brown iron stone rubble" (HUNDT et al. 1887), accompanied by pale ores, zinc blende (sphalerite) and copper pebbles (chalcopyrite) in a gangue of quartz, greywacke and slate. However, the mineralization was apparently not productive and regular enough for profitable mining. The upper tunnel with the dump and a small pinging train can still be located in the area today, only a few remains of the dump can be found of the deep tunnel.
A first comprehensive article on the minerals in this pit was published by MANDLER et al. in 1989. They reported some very interesting mineral finds from the heaps, including large sphalerite and pale ore crystals, solid silver and rarities such as cuproadamine and gerhardtite. MANDLER et al. considered their article to be a “preliminary interim result”, as the secondary mineralization turned out to be very species-rich and other questionable minerals were waiting to be determined. Soon afterwards the minerals bindheimite (today oxyplumboroméite), scorodite and suzannite were added (ANONYMUS 1989). Redgillite and zinc olivenite were added later (SCHNORRER et al. 2006; GRÖBNER & KOLITSCH 2009) and further show that an extraordinarily diverse paragenesis occurs here. Our collecting activities and investigations have shown a large number of the species already described, but also some completely new minerals for the site. The minerals newly determined in the context of this article were examined as far as possible with both Raman spectroscopy and EDX.
Profile plan of the pit Schöne Aussicht from 1902. Side view of the shaft, upper gallery and the deep gallery floor. Archive: Henry Weskamp, Burbach
Nice sphalerites and rare ores
The deposit of the Schöne Aussicht mine shows similarities in some respects with the deposits in the Buchhellertal, but above all with the Grüne Hope mine. Quartz is the main gangue of the occurrence and also forms crystals up to 1 cm in length in cavities. The ores sought in the Schöne Aussicht mine were galena, sphalerite, pale ore and chalcopyrite, which occur in coarse nests and strings in quartz, brown iron ore, slate and greywacke. The brown iron ore turns into siderite with increasing depth.
Particularly noteworthy are the large, dark to honey brown, partly splendidly translucent sphalerite crystals up to approx. 2 cm in size. They appear on quartz and greywacke next to small siderite crystals. They can have spear-point marcasites up to 2 mm in length. The pale ores tetrahedrite and tennantite as well as chalcopyrite, galena and pyrite occur in partly well-developed crystals.
The tetrahedrite and galena can reach sizes up to 1 cm, while tennantite, chalcopyrite and pyrite form crystals up to approx. 3 mm in size. It is not easy to distinguish the two pale ores from one another.
Tennantite shows red internal reflections in thin splinters.
It is not uncommon to find ullmannite grown in quartz in cube-shaped crystals and aggregates up to
approx. 5 mm edge length. The nickel ore, which has been known from the neighboring Green Hope mine for two centuries (ULLMANN 1814), was grown up freely, but only rarely and then mostly very small and already corroded. Gersdorffite, which can hardly be distinguished visually from Ullmannite, was also redefined. It forms coarse ore slugs in the quartz as well as rarely very small large-area crystals in drusen, which, in contrast to ullmannite, tend to become darker.
From the hydrothermal decomposition of the ullmannite in a more recent mineralization phase, the occurrence of millerite results in small brass-yellow metallic needles up to approx. 5 mm in length. Like the ullmannite, they are mostly enclosed in the quartz, but sometimes also protrude into cavities and sometimes spear through fahler ore crystals. Siegenite is a new determination and shows itself as a great rarity in very small silver-white octahedra.
Another special feature is the new find of bournonite, not because the crystals are particularly beautiful and large, but because this mineral was not previously known in the Burbach deposits. The large-area crystals reach a maximum size of 2 mm and sit on quartz.
The intimate intergrowths and displacements of sulphide ores are sometimes very complex in the area of the Schöne Aussicht mine. ADELMANN (2014) is an example of how younger Fahler ore is displacing chalcopyrite at the edges. Fahlerz also forms thin seams around ullmannite relics, embedded in galena with chalkopyrite embedded in it, which in turn contains enclosed millerite needles.
Furthermore, rounded bournonite grains could be discovered in ore cuts as small inclusions in the coarse tetrahedral, so they are probably older than the pale ore (personal communication H. ADELMANN, 2019). Ullmannite, chalcopyrite, millerite, "copper luster" (predominantly diginite) and the minerals famatinite and vaesite, which are very rare for the Siegerland as idiomorphic, ingrown crystals, are further components of this complex paragenesis. The intergrowth of the famatinite with the copper luster, the partly colloidal form of deposition of the copper luster, the corrosion of the chalcopyrite and the displacement of the pale ore by famatinite indicate that both famatinite and the copper luster are supergeneric (cementative) genesis and thus younger than pale ore and chalcopyrite (personal communication by H. ADELMANN, 2019).
From SCHNORRER et al. In 2006, instead of digenite, chalcosine was also mentioned, which, like bornite, displaces the coarse chalcopyrite.
Tetrahedrite on quartz. Image width: 7.5 mm. Collection: Matthias Reinhardt, Drolshagen.
Tetrahedrite on quartz. Image width: 3.8 mm. Collection: Matthias Reinhardt, Drolshagen.
Tetrahedrite on quartz. Image width: 6 mm. Collection: Matthias Reinhardt, Drolshagen.
Ullmannite in quartz. Image width: 13.5 mm. Collection: Matthias Reinhardt, Drolshagen.
Bournonite on quartz. Image width: 4.7 mm. Collection: Matthias Reinhardt, Drolshagen.
Galena. Image width: 7 mm. Collection: Matthias Reinhardt, Drolshagen.
Galena. Image width: 3 mm. Collection: Matthias Reinhardt, Drolshagen.
Silver in limonite. Image width: 1.5 mm. Collection: Jörg Mandler, Wetzlar.
Silver on limonite. Image width: 1.8 mm. Collection: Jörg Mandler, Wetzlar.
Chalcopyrite on quartz. Image width: 3.6 mm. Collection: Matthias Reinhardt, Drolshagen.
Millerite with morenosite. Image width: 4 mm. Collection: Matthias Reinhardt, Drolshagen.
Rare arsenates displace mimetite
In many cases, mimetite and cerussite are covered by younger, often crusty, finely crystalline or globular minerals and in some cases displaced as pseudo or paramorphic. In addition to goethite, these include above all linarite, malachite, brochantite, segnitite, cuproadamine and bayldonite. The copper-containing adamin (variety cuproadamin) has been known since the 1980s (MANDLER et al. 1989), which forms light-, olive- or apple-green spherical-kidney crusts and aggregates, some of which consist of tiny crystals, on mimetite and quartz. Cuproadamin can hardly be distinguished from its close relatives zinc olivenite and olivenite. Zinc olivenite, which is an independent link in the Adamin - olivite series with a Cu: Zn ratio in the range between 1: 3 and 3: 1, occurs in the form of green, shiny, spherical aggregates up to 0.5 mm (GRÖBNER & KOLITSCH 2009). The copper end link of this series, the olivite, was also found in the Schöne Aussicht mine. It forms small olive-green crystals that line turf-like cavities in the quartz.
Bayldonite is visually similar to cuproadamine, the color of which is usually a little darker green. It also forms green crystalline crusts that cover quartz, brown iron stone and mimetite. Intense yellow crystalline coatings and spherical aggregates have been found to be segnitite. They are composed of innumerable pointed rhombohedral crystals, are relatively common and sometimes form pseudomorphoses like older mimetite crystals. In the investigations with Raman spectroscopy and EDX, no sulfate content could be detected, so that the segnitite can be clearly differentiated from beudantite.
Scorodite, which we could not find ourselves, is mentioned as small crystals (ANONYMUS 1989). Instead, we were able to identify pharmacosiderite in tiny light yellow pseudo-cubic crystals.
What is special is that the pharmacosiderite from Grube Schöne Aussicht has significant lead contents that are close to the composition of plumbopharmacosiderite. Presumably there are intermediate mixed crystals between the two. It has not yet been possible to check whether there is also a zonal construction of the two minerals.
"Young savages" in the dump material
Very species-rich and with many rarities, a paragenesis emerges in the mineral stock of the Schöne Aussicht mine, which at least for the most part only arose in the heap material. For the heaps of lead-copper-zinc mines typical minerals with crystals are consistently in the micro range, as they have meanwhile been observed in many places. Anglesite and cerussite belong in small crystals. The cerussites rarely appear slightly bluish. Light yellow, almost transparent crystals of solid sulfur are occasionally found together with angelsite in the vicinity of corroded galena. Leadhillite and susannite occur as pseudo-hexagonal tabular crystals up to millimeter in size. Most of them are colorless to cloudy white, susannite is also described as yellowish (ANONYMUS 1989). As described by other sites, it can be assumed that here, too, at least some of the paramorphoses are from Susannite to Leadhillite. Leadhillite / Susannite are usually accompanied by caledonite. Due to its greenish-blue color, this is somewhat more conspicuous and forms long prismatic crystals, which are usually aggregated in the shape of sheaves and tufts. Covellin often shows up together with these minerals as blue-black metallic coatings and small flaky pustules on the weathering sulfides.
Basic copper sulfates are another typical representative of this mineral society. Langite and posnyakite were found quite frequently in the material from the Schöne Aussicht mine, they are light to ink blue in color and difficult to distinguish from one another. Langite crystals often show short prismatic, blocky and often six-sided shapes and reach a size of about 2 mm. Posnjakit appears in tabular, leafy, often diamond-shaped or pointed forms. As at other sites, transitions from langite or posnjakite to brochantite can be observed here, which manifest themselves in zonal to completely cloudy green colorations of the crystals. Brochantite itself forms emerald green tabular, partly tongue-shaped crystals and crystalline crusts. A mineral that has not been known for very long is redgillite. This occurs with preference in the company of Langit and / or Posnjakit. It is therefore not surprising that the fine, light-green and grass-green needles up to 1 mm in length could also be found in the heap material of the Schöne Aussicht mine (SCHNORRER et al. 2006). They are composed of tufts, pustules and sheaves that have always formed in the vicinity of chalcopyrite, which according to SCHNORRER et al. is almost always partially converted into bornite or chalcosine. Serpierite is used by SCHNORRER et al. named as an accompanying mineral of redgillite without further description. With Devillin, a closely related and chemically and visually very similar mineral could be detected in light turquoise-blue ledge-shaped crystals. This is also a redefinition for the site like ktenasite, which forms bluish-green tablets (<0.5 mm) and has a high nickel content. Both occur together with brochantite and linarite on quartz, brown iron ore and weathered lead and copper ores. Turquoise-green schulenbergite leaflets that have grown together to form small rosettes have been observed very rarely (GOLZE et al. 2012). Another very rare aluminum-containing copper sulphate is spangolite, which forms the characteristic pointed six-sided crystals (<0.5 mm) of blue-green color on a few finds. A very unusual mineral is that of MANDLER et al. (1989) described copper nitrate Gerhardtite, which forms apple-green, radially arranged tabular crystals up to 0.5 mm in size near weathered copper ores.
Globular malachite also occurs again as heaps. Rosasite is quite similar to this, but its spheres measuring only 0.2 mm have a rather blue-green color. MANDLER et al. (1989) were able to detect this copper-zinc carbonate by X-ray analysis. The rosasite beads grew up on cuproadamin. Intense light blue, radial-rayed spheres up to 0.5 mm in diameter, which sit together with cerussite, mimetesite and posnjakite on quartz, sphalerite and pale ore, turned out to be the very rare sulphate and arsenate-containing copper-zinc carbonate Claraite - a first find for the Siegerland. The white, needle-like crystal clusters of aragonite and the long-tabular, typically formed gypsum crystals measuring up to 3 mm were also formed as new formations in the heap material; also white scaly leaves of hydromuscovite ("sericite") on quartz. Amorphous smooth kidney crusts of blue-green color can be assigned to the allophane, which was already used by MANDLER et al. (1989). White, powdery interstitial fillings in quartz, siderite and greywacke made of kaolinite and / or dickite are quite common, but have not been investigated further.
The widely occurring nickel ores ullmannite, gersdorffite and millerite provided the material basis for the formation of a number of other minerals. Ullmannite crystals that have grown into quartz are occasionally completely or partially displaced by white, yellowish or greenish stibiconite, as has already been observed at other Siegerland sites (e.g. Grube Brüderbund; HENRICH 1996). Bottinoite is a characteristic decomposition product of Ullmannite in the dump material. The nickel-antimony hydroxide could also be found in the typical blue-green, translucent and mostly rounded-edge tablets (<0.5 mm) on the steps from the Schöne Aussicht mine. The weathering of the Gersdorffite resulted in annabergite in light green spherical-kidney-shaped aggregates. The closely related Köttigit forms rosette-like and cluster-like aggregated strip-shaped crystals. Both Annabergit and Köttigit show a clear copper content, which indicates a mixed crystal formation with Babánekite, which has not yet been dominant. Rare green pseudomorphoses after Millerite needles turned out to be the relatively rare nickel hydroxide sulfate jamborite. Comparable pseudomorphoses from other Siegerland sites were identified and described as morenosite more than two decades ago (HENRICH 1996; REINHARDT 1997).
When, in 2013, a similar historical stage by Pfannenberger Unity near Salchendorf in the collection of Harvard University (Cambrigde / Massachusetts, USA) was analyzed and published as jamborite (ALONSO-PEREZ & WARMINGTON 2013), the first doubts arose. In the case of the Schöne Aussicht mine, the jamborite has now been confirmed. The Raman spectrum fits well with jamborite, the EDX result with restrictions, since superficial impurities are presumably present. Such impurities could also have been the decisive factor in incorrect determination in the samples from the other Siegerland sites. A new review of these samples is still pending.
In summary, it can be said that the Schöne Aussicht mine near Burbach is one of the most species-rich sites in the Siegerland. There are still some question marks unanswered and it can be assumed that some collections still contain other species that are new to the site. Overall, through our own collections and with reference to the more recent literature, we were able to list 71 different mineral types for this site - including rarities such as bayldonite, bottinoite, claraite, gerhardtite, jamborite, ktenasite, redgillite or zinc olivenite.
Regarding the current find situation, it must be said that the heaps and outcrops in the area of the Schöne Aussicht pit are now heavily searched and no longer very productive. No wonder, since the site was already intensively collected in the 1980s. With a lot of luck, however, some of the minerals described here can still be found in document quality on the heap of the upper adit, for example mimetesite, cerussite, langite and the ullmannite enclosed in quartz. Not far from the Schöne Aussicht pit, on the top of the castle hill, there was a Celtic hill fort from pre-Christian times, of which the remains of a ring wall can still be found in the forest. This old Keltenburg has nothing to do with the mine itself, but it gives the mountain its name. The sites not far away in Buchhellertal have also been heavily searched. However, all of the pits are located in a historically, scenic, mineralogically and geologically attractive area, in which both mining and long-extinct volcanism have left plenty of traces and outcrops that can be discovered on long hikes.