Comments Off on Excursion to Slanské a Zemplinské vrchy 2024
The excursion took place from 24.4.-28.4.2024 in the locality of the neovolcanic Slanské vrchy mountain range, which extends in the eastern part of Slovakia east of the city of Prešov and with its length of 100 km extends to the territory of neighboring Hungary. The Slovak part of the mountain range consists dominantly of andesite stratovolcanoes reaching heights from 800 m.a.s.l. up to 1092 m.a.s.l., which stretch in a crescent-shaped chain from north to south. They were formed at the fault interface between the tectonic units of the Západní Karpaty (gemerikum, fatrikum) in the west and hard-to-classify units in the east – zemplinikum, Pozdišovsko-Inačovská unit. The first magmatic activity is dated to the Lower Miocene as a result of the Alpine orogeny. The well-recognizable stratovolcanoes include, from north to south: Šťavnica, Zlatobáňský, Makovica, Strechovy vrch, Bogota, Hradisko, Bradlo and Velký Milič. During their formation, parts of them also underwent significant hydrothermal transformation, during which ore and opal mineralization were established.
some visited localities:
Zlatá Baňa – Zlatobansky stratovolcano – 140 types of minerals described -polymetallic (Mo-Cu-Pb-Zn-Ag) and antimony mineralization – antimonite, amethyst, bournonite, boulangerite, metastibnite, cinnabarite, galena, pyrite
Fig. 1 – Zlatá Baňa locality
Dubnik – the southern part of the Zlatá Baňa stratovolcano – the formation of mineralization in andesite lava flows by post-magmatic hydrothermal activity – significant deposit of opals (precious, milky, hyalit) -historical mining of cinnabarite as an ore of mercury
Fig. 2 – Dubnik precious opal
Herlany -Strechový vrch stratovolcano – the famous mäsovy opal of a brown-red color
The next part of the excursion took place in an elevation formed by Permocarbon continental sediments with anthracite and thick layers of tuffs – the Zemplinské vrchy. It is a synclinal structure of a complex structure consisting mainly of highly metamorphosed rocks (mainly gneisses, amphibolites).
Byšta – Brezina -near the Velký Milič stratovolcano – agates, chalcedony
Velká Trňa – the western slope of the Zemplinské Vrchy -Anthracite
Fig. 3 – Excursion checking the geological map in the field
Comments Off on SGA Student Chapter Prague autumn field trip to the Ore Mountains, Czech Republic (petrological overview, mining history, and current mineral deposits)
Jan Kamenský1,2, Jan Kulhánek1
1Faculty of Science, Charles University, Prague, Czech Republic 2Czech Geological Survey, Prague, Czech Republic
The SGA Student Chapter Prague honours its long-standing tradition of organizing an annual autumn field trip, and this year was no exception. Scheduled for late autumn (November 17–19, 2023) the trip was strategically planned to allow the participation of first-year bachelor geology students. Our destination of choice this year was the captivating mineralogical sites and historically significant localities of the Ore Mountains in the NW Czech Republic. Sixteen students participated in the excursion, led by chapter advisor Dr. Jan Kulhánek and president Jiří Klepp.
Geological settings: The European Variscan Belt finds its easternmost exposure in Central Europe, shaping the Bohemian Massif. The Ore Mountains, a historically significant mining region, are situated within the Saxothuringian Zone (SZ), the SW–NE-trending belt which extends in the NW part of the Bohemian Massif (see Figure 1). The SZ is tectonically separated from the Teplá-Barrandien unit (TBU), lying along its southeastern border. Within this framework, the SZ represents the lower plate that underwent subduction beneath the hanging wall of the TBU along a prominent Variscan suture (e.g., Franke, 1989; Jouvent et al., 2022). Comprising primarily complexly over-thrusted and over-folded metamorphic nappe units of diverse metamorphic grades, the Ore Mountains exemplify accretionary wedge formation between the SZ and TBU. From the deeper levels of the subduction channel, rocks of high- to ultra-high-pressure metamorphism, such as eclogites, blueschists, and coesite- or diamond-bearing paragneisses and granulites, have been exhumed (see Jouvent et al., 2022). The Variscian and post-Variscan tectono-magmatic activities are closely associated with the formation and subsequent remobilization of the polymetallic ores in the area. The Bohemian Massif also underwent significant magmatic and volcanic activity during the Cenozoic era. Much of this volcanic activity was concentrated along the Eger Rift, aligning with the Saxothuringian Variscan suture, and constituting the northeastern branch of the European Cenozoic Rift System (Ulrych et al., 2011). Evidence of this volcanic activity is also observable in the Ore Mountains, where well-preserved remnants of Cenozoic volcanism, erupting through the metamorphic basement, form prominent hills in the surrounding landscape.
Figure 1. The schematic geological map of the Saxothuringian Zone according to Faryad & Kachlík (2013).
1st day: The field trip began at the hut at Boží Dar, an old mining town near the Czech-German border, on the evening of November 16, 2023, which served as our base for the entire excursion. The following morning, November 17th, visit of several localities followed after the broad geological introduction at the hut. Our first visit took us to Abertamy town, where we visited private collection of mining artifacts and ore minerals sourced from the surrounding localities, such as Abertamy, Jáchymov, or Stříbro.
Continuing our trip, we embarked on a brief tour of the surrounding of the closed Mauriticius mine, the oldest tin mine in the Czech part of the Ore Mountains, with its origins tracing back to the 16th century. This historical site, now open for tourists, offered a glimpse into centuries-old mining practices. Our time at the Mauriticius mine also afforded opportunities for mineralogical sampling, with notable finds including specimens of hematite and quartz (amethyst variety) sourced from the mine’s excavation sites and observation of the metasomatic process causing formation of greisens and associated tin mineralization along the veins cutting the granitic body. In the vicinity of the Mauritius mine was also possible to observe Schnepp’s pinge, a sinkhole formed atop the remnants of a former tin mine, following the steep vein planar orientation. In the vicinity of the Mauritius mine was also possible to observe Schnepp’s pinge, a sinkhole formed atop the remnants of a former tin mine, following the steep vein planar orientation.
Our itinerary then led us beyond the confines of the Ore Mountains to the significant mineralogical site of Huber Stock, situated near Horní Slavkov (GPS: 50° 8′ 19″ N, 12° 48′ 28″ E). Geologically characterized as a greisenized plutonic elevation, Huber Stock stands as a testament to the region’s diverse mineral wealth, with notable occurrences of tungsten and tin mineralization. Historical records indicate subsurface mining activities dating back to the 13th century, with a notable period of pit quarry operations from 1973 to 1976. Notably, Huber Stock boasts a rich mineralogical diversity, with 117 documented minerals, including five designated type localities, underscoring its significance in the field of mineralogy.
2nd day: Our second day of the trip began with a visit to Meluzína Hill, a prominent feature in the landscape. Comprised mainly of eclogite, a high- to ultra-high metamorphic rock, Meluzína Hill offers insights into the region’s geological history. Originating from the subducted oceanic Saxothuringian plate, the rock was subducted deep beneath the TBU plate into the Earth’s mantle before being exhumated back to the crustal levels, shedding light on past plate tectonic processes. Discussions at the site focused on reconstructing the pressure-temperature conditions that shaped these rocks, along with an examination of the “atoll texture” of garnets commonly observed in metamorphic rocks of the area.
Our journey then took us to Horní Halže, where we explored remnants of iron ore mining. Here, a small heap served as a reminder of the area’s industrial past, with quartz veins often displaying a distinct violet color, earning the site the nickname “Amethyst heap.”
Next, we visited Mědník Hill in Měděnec, where iron ore extraction occurred from the 15th to the 19th century. The site’s skarn body, associated with the polymetallic mineralization, showcased visible garnet, diopside, and magnetite grains, providing insights into the region’s mining heritage.
Finally, we arrived at Volyně u Kadaně, a forested area housing loose rocks indicative of mining activity focused on a quartz hydrothermal vein renowned for the associated fluorine and tungsten mineralization. Characterized by a brecciated and honeycombed texture due to fluorite leaching, the vein revealed small fluorite and scheelite crystals, well-recognizable under the short-wave UV light (Figure 2).
Figure 2. Photo of collected scheelite-rich samples from the site Volyně u Kadaně under short-wave UV light. Photo by A. Ignasheva.
3rd day: Our final day began with a visit to the Kovářská site, where we examined fluorite-barite veins that were actively mined in the 1970s and 1980s. Though mining activities have ceased, remnants of these veins remain, offering opportunities for mineral collection. Participants had the chance to collect specimens of fluorite and barite from surrounding mining heaps, providing tangible connections to the area’s mining history. Moving on, we also visited a reclaimed heap near Hradiště u Kadaně, focusing on collecting hematite crystals, characteristic of the area. Our excursion concluded at the Blahuňov locality, known for hydrothermal veins cutting through gneiss formations. Here, participants observed collectible fluorite-quartz specimens, with the quartz exhibiting a carnelian variety.
With our cars loaded with mineral samples, we concluded our excursion and returned to Prague, reflecting on our experiences over the past three days. Our exploration had not only yielded valuable specimens but also deepened our understanding of the mining and geological history of the Ore mountains.
Figure 3. Group photo in front of the historical mining gallery in Měděnec. Photo by J. Klepp.
Acknowledgments: We wish to extend our gratitude to the company Severočeské uhelné doly a.s. and to the UNESCO International Geoscience Programme (project ČNK-IGCP 637) for their financial support.
References: Faryad, S. W., & Kachlík, V., 2013. New evidence of blueschist facies rocks and their geotectonic implication for Variscan suture (s) in the Bohemian Massif. Journal of metamorphic Geology, 31(1), 63–82.
Franke, W., 1989. Tectonostratigraphic units in the Variscan belt of central Europe. Geological Society of America Special Paper, 230, 67–90.
Jouvent, M., Lexa, O., Peřestý, V., & Jeřábek, P., 2022. New constraints on the tectonometamorphic evolution of the Erzgebirge orogenic wedge (Saxothuringian Domain, Bohemian Massif). Journal of Metamorphic Geology, 40(4), 687–715.
Ulrych, J., Dostál, J., Adamovič, J., Jelínek, E., Špaček, P., Hegner, E., & Balogh, K., 2011. Recurrent Cenozoic volcanic activity in the Bohemian Massif (Czech Republic). Lithos, 123, 133–144.
Comments Off on SGA Keynote speaker Professor Hartwig E. Frimmel in Prague
Jan Kulhánek1,2
1SGA Student Chapter Prague 2Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Prague, Czech Republic
The SGA Student Chapter Prague was honoured to host a seminar for the entire geological section of the Faculty of Science, Charles University in Prague, featuring Professor Hartwig E. Frimmel from the University of Würzburg, Germany. The lecture, held on November 3rd, 2023, drew a diverse audience ranging from bachelor students to professors, reflecting the broad appeal of the topic, “Giant Impacts and the Formation of Ore Deposits,” within the geological sciences community.
The presentation was supplemented with a succinct annotation: “Some of the largest impact sites known on Earth overlap in space with exceptional concentrations of ore deposits. This has led to speculations on a potential addition of extraterrestrial metal compounds to the Earth’s crust on an economic scale. Using the three largest impact structures as reference, the likely controls of large impacts on metallogeny will be discussed, and it will be shown that metal endowment is strongly controlled by the regional geological make-up of the crust prior to impact.”
Inviting Professor Hartwig to our faculty provided a unique opportunity not only to hear his lecture but also for students to engage with a renowned figure in the field of geology. To underscore the significance of Professor Hartwig’s contributions, we would like to share a brief overview of his biography:
Hartwig E. Frimmel, who obtained his PhD in geology at the University of Vienna, is Professor and Chair of Geodynamics and Geomaterials Research at the University of Würzburg, Germany. He is also associated with the University of Cape Town where he had previously climbed the academic ladder from lecturer to associate professor. He was leader of the Earth Science subprogram within the South African National Antarctic Program, member of the Geoscience Scientific Standing Committee of the Scientific Committee on Antarctic Research (SCAR), former president of the Society for Geology Applied to Mineral Deposits (SGA), and director of Lithoscope consultancy. He has served on several editorial boards (incl. Mineralium Deposita for the past 23 years), on the International Commission on Stratigraphy, as assessor for numerous national research funding and government agencies, and as consultant to mining/exploration companies as well as government bodies. His research interests developed over more than three decades from metamorphic geology and fluid-rock interaction to metallogenesis and economic geology. A special focus has been the study of sediment-hosted base metal and gold deposits, especially those of the Witwatersrand-type. His research output includes more than 200 articles and book chapters as well as three books.
After the lecture, an engaging discussion was organized in the meeting room of the Institute of Petrology and Structural Geology, providing students with the opportunity to further delve into the topics covered by Professor Frimmel’s presentation. Against the backdrop of pleasant refreshments, students exchanged ideas and posed questions, enriching their understanding of the subject matter and discovering more about the Prof. Frimmel broad experiences from the world. Later in the evening, a dinner meeting was organized at a local restaurant, bringing together representatives from the SGA (Hartwig Frimmel and Anna Vymazalová, members of the SGA Executive Committee, and Prague Chapter representatives) for further networking and discussions. This gathering offered an informal setting for participants to connect with SGA representatives, facilitating valuable exchanges of ideas and insights. We extend our gratitude to Professor Frimmel for his engaging lecture and enthusiastic participation in post-seminar discussions. Our gratitude belongs to the SGA, namely SGA Keynote Speaker Program, and the Geological Section of Charles University for generously supporting the organization of this event. Their contributions made it possible to host Professor Frimmel’s lecture and facilitate enriching discussions and networking opportunities, enhancing the academic experience for all participants.
Figure 1: Flyer for the event used at the Faculty of Science, Charles University.Figure 2: After-seminar discussion in the meeting room of Institute of Petrology and Structural Geology.Figure 3: After-seminar discussion during the related sport activities.
Comments Off on SGA Student Chapter Prague – The 20th Anniversary
Since 2022 is the year of celebrations for the SGA Student Chapter Prague, we have decided to organize the annual SGA Prague Christmas meeting and the 20th Anniversary celebration on 7th December. The event took place at the Faculty of Science, Charles University. On the same day we organized an excursion to the gold mine near Jílové u Prahy took place for those interested.
SGA
The Society for Geology Applied to Mineral Deposits (SGA) is an international scientific society that promotes the science of mineral deposits. The society consists of over 1300 members among researchers, professionals and students from universities, industry and governments interested in economic geology, mineral resources, industrial minerals and environmental aspects related to mineral deposits. SGA regularly organizes conferences, international courses and workshops. The next SGA Biennial Meeting will be held in Zürich, Switzerland between 28th August and 1st September 2023. An integral part of the organization is the long-term support of geoscience students through the SGA Educational Fund.
History of the SGA Student Chapter Prague
This year marks exactly 20 years since several students from Charles and Freiberg Universities founded the first-ever SGA Student Chapter. In 2002, a joint Prague-Freiberg Chapter was established by Dr. Anna Vymazalová and Dr. Alex Otto, both master students at the time. This newly formed Chapter’s first event was an excursion to the Svornost mine in Jáchymov, Czech Republic in April 2003. Subsequently, a division occurred and the independent SGA Student Chapter Prague was established. Despite the difficulties during the years 2020 and 2021 caused by the COVID-19 pandemic, the SGA Student Chapter Prague has around 70 members.
This year, we celebrate two significant anniversaries simultaneously—the 20th anniversary of the existence of the SGA Student Chapter and the 10th president in office.
SGA Student Chapter Prague Christmas meeting
We are pleased that 83 SGA supporters from the Czech Republic, Germany, Portugal, Spain, Switzerland and Slovakia gathered for the anniversary celebrations. Eleven of them took part in the international field trip. The official program in the Mineralogical lecture room started at 4:30 p.m. with an opening speech by President Jan Kamenský. This was followed by a lecture by Ivan Mateo Espinel Pachon from the University of Geneva on the topic: “Controlling the redox evolution of arc magmas on continental margins: an approach to melt inclusion”. This lecture has followed a presentation by Dr. Anna Vymazalová, one of the founders of the SGA Student Chapter Prague, with her talk on the history of the SGA Student Chapter Prague. Afterwards, representatives of the student associations SEG-SGA Barcelona and SGA Colombia-Bogóta gave a short presentation of their activities and encouraged students to cooperate internationally. After the presentations, we visited the Mineralogical Museum of the Faculty of Science and the Chlupáč Museum. The entire program ended with a meeting in the Malé sbírky lecture room, where we had a unique opportunity to discuss plans for upcoming years.
Fig. 1 – Excursion to the Pepř mine near Jílové u Prahy, author of the photo: Jan MráčekFig. 2 – Tour of the Mineralogical Museum at the Faculty of Science, author of the photo: Jan Mráček
We would like to thank our sponsors, without whose help the organization and provision of the program would be very complicated. In particular, we would like to thank the Faculty of Science of Charles University, Řeznictví Jiří Görgl (Butchery Jiří Görgl), Pekařství Kabát (Bakery Kabát) and the Vinařství Cenek (Winery Cenek).
Comments Off on A field-trip to the gold mining district in Jílové, Czech Republic
Václav Santolík
“Everything is functional here,” says Vladimír Pravda showing us his “office” 300 meters below ground, where we got by a minecart. He is a member of a group of enthusiasts that bought the dilapidated Jílové mines a few years ago. With his coworkers, he spends weekends on restoring the clogged stoles and abandoned machinery.
Fig. 1 – Observation of gold-bearing quartz veins in the Jílové Mine.
Gold mining has a long tradition in the Czech Republic. There are several historically famous mining districts like Jílové, Mokrsko, Kašperské Hory and Zlaté Hory. Unfortunately, all have been shut down during or shortly after the communist era. Currently exploration is proceeding at Zlaté Hory, however, the local socio-political situation does not favor any reopening of old mines.
The Jílové gold-bearing district was one of the most important areas of historical gold mining in Bohemia. The tradition of panning dates back to the period of Celtic settlement. In the 13th and 14th centuries, when gold was obtained mainly by deep mining with a total production of approximately 10 tons of gold, the Jílové district was probably the most profitable gold-bearing district in the Kingdom of Bohemia. Unfortunately, the mines with all documentation have been burnt during the husite wars in the 15th century. The profit from reopening in the 16th to 19th century and in the years 1938 – 1968 was not even close to that of the medieval times. Finally, the geological studies from the 1960s concluded that the mining would no longer be profitable.
The fame of the Jílové district may have been based on the fact that gold was often found here in the form of coarse-grained aggregates and irregular sheets weighing up to several kilograms. The gold is present in quartz and quartz-carbonate veins, often accompanied by sulfides (pyrite, arsenopyrite, etc.), tellurium and bismuth minerals, scheelite, etc. Gold-bearing deposits usually have simple mineral composition, however, 51 minerals have been described from the Jílové district – many of them are rare, often detectable only during microscopic research.
Fig. 2 – Happy visiters of Jílové Mine at the end of excursion.
After several hours under ground, Vladimír wanted to provide us with some hands-on experience. “The country rock is very hard here, therefore, dynamite was used for digging the stoles. Here is a trigger that they used: you just need to spin the arm several times and push this button when it starts to blink,” he passes a small box to my friend. After my friend pushed the button, a staggering bang froze us. “I told you everything was functional here,” claimed Vladimír calmly. “This way, please. Before the smoke and dust reaches us.”
Comments Off on Fieldtrip report: Zlaté Hory deposits and history of mining
Fig. 1: Participants of the fieldtrip. Photo by V. Santolík.
At the end of October 2021, the SGA student chapter in Prague held a three-day autumn excursion focused on a mining district Zlaté Hory in Jeseníky mountains and its surroundings. The area is composed of Variscan metamorphic rocks like phyllite, micaschist, paragneiss, orthogneiss, amphibolite and limestone, which were formed from Cadomian (~570 Ma) to Variscan (~300 Ma) times. The polymetallic VHMS deposit occurs in metamorphosed Devonian formations and is currently a matter of exploration for possible gold mining.
1st day. History of Au, Fe and Mo mining in the Zlaté Hory region.
The first day was focused on surface signs of previous mining and was lead by Dr. Josef Večeřa. These are dominated by placer mining marks like pits, hollows and canals as well as underground mining marks like pits and adits. The researchers were able to define three stages of mining based on different mining techniques – medieval, modern and 19th century. Interestingly, the different stages are commonly seen at a single locality. For example, in Hláska forest near Ludvíkov village, there are several pits following a single ore bearing structure and depending on the distance between particular pits, it can be inferred, whether they correspond to the medieval or modern period. Consequently, we visited a locality near Vidly village where we found several minerals related to iron ore which was mined until 18th century, including magnetite, hematite, specularite and jasper.
2nd day. Minerals collecting in mine Zlaté Hory – west; “Blue drift”.
On the second day, we went down into the Zlaté Hory – west mine, where the current exploration takes place. The walk to the end of the drift was nearly 4 km long, unfortunately the oxygen level detector did not allow us to stay there for a longer time and search for minerals. However, during the 4-kilometer walk we still managed to find several appealing minerals, for instance pyrite, galena, sphalerite, cerussite and copper. On the way back, we entered the “Blue Drift”, which is called blue for the intriguing blue colored allophane covering the walls. After a few hours in the mine, we visited local museum with a nice exposition of minerals and rocks found in the area.
Fig. 2: Azure blue allophane covering walls in the “Blue Drift”. Photo by V. Santolík.
3rd day. History of mining – open-air museum.
On the third day morning, we visited an outdoor museum dedicated to old miners and old mining techniques. We learned about their lifestyle and tools they used for daily life as well as the methods and equipment applied for gold obtainment. At the end, we were encouraged to find some gold with a gold washing pan in the arranged containers with sand and water. The most adventurous of us could not resist despite the freezing water and managed to find a few gold grains. Finally, with minds full of new experience and bags full of new minerals, we returned back home.
Fig. 3: Gold mining open-air museum in Zlaté Hory. Photo by V. Santolík.Fig. 4: Collected quartz sample with a native gold. The biggest gold has a size of 200 µm. Photo by M. Tuhý.
Děkujeme IGCP 682 – MINE TAILING REVALORIZATION (Duration: 2019-2021) za finanční podporu, která přispěla k organizaci této exkurze / We thank IGCP 682 – MINE TAILING REVALORIZATION (Duration: 2019-2021) for its financial support, which helped to organise this excursion.
Štěpán Jaroměřský; Karolína Fizková; Jan Šulc; Štěpán Dvořák; Marek Tuhý
Faculty of Science, Charles University, 128 43 Praha 2, Czech Republic; Corresponding author E-mail address: jaromers@natur.cuni.cz
Fig. 1: Ongoing lecture; Photo by Štěpán Jaroměřský
On 30th July was organized, despite some restrictions caused by the pandemic, excursion to South Bohemia. 15 Chapter members took part in this 1-day excursion. The expert interpretation was led by Mgr. Miloš Faltus, Ph.D. (Fig. 1). The aim of the excursion was to introduce the participants to the Czech rarity in the form of tectite called Moldavite. As one of the few people we were given the opportunity to look into the sand pit (Fig. 2), which is located between the village of Chlum and Ločenice. This sand pit is mainly used for sand mining, but its secondary product are the Moldavites (Fig. 3). It is the only company in the Czech Republic that has permission to officially mine and then sell Moldavites
Fig. 2: View of the sandpit; Photo by Jan ŠulcFig. 3: Active treatment plant; Photo by Jan Šulc
The first discovery of Moldavites was in 1787 by Dr. Josef Mayer from Charles University. He had thought of them as glass of volcanic origin. They were named after the Vltava River, around which the first findings were located. Later, the concept of Moldavite was introduced from German Moldau (Vltava). As similar glasses were later found more widely around the world, the common international name of tectite (from Greek tectose – fused) was also used for them. Generally they are vitreous bodies, which usually have dimensions of several centimeters and a weight of several units up to tens of grams. Tectites can be found all over the world, but Czech Moldavites, unlike others, have a transparent light or dark green colour.
Today, the most likely and widely accepted theory of the formation of Moldavites is considered to be the impact of a meteorite on the surface of the Earth some 14.5 million years ago. This impact occurred in the area of today’s so-called The Ries crater between Norimberk, Stuttgart and Munich. Today in the centre of this crater lies the city of Nördlingen. The Ries crater is 24 km in diameter. The meteorite impact occurred at a speed of about 20 km/s, at an impact angle of 30-50 °. During the collision with the Earth, a huge amount of energy was transferred, resulting in the crushing, melting and evaporation of rocks at the point of impact as well as a separate cosmic body. There was a cloud containing gaseous, liquid and solid phases, the main part of which was directed to the East. When the initial high temperature and pressure dropped, the silicate melt solidified so quickly that the individual mineral components did not fully crystallize to form silicate glass. This was particularly the case in the area of southern Bohemia and southern Moravia in the vicinity of Trebic. The range of the vltavins from Ries crater to southern Bohemia and southern Moravia was 200-450 km. It is estimated that the total weight of all fallen vltavins would be about 3000 tonnes.
Fig. 4: Currently found moldavite; Photo by Jan Šulc
South Bohemian Moldavite is characterised by its light – dark green colour. This is different from the Moravian ones, which tend to be in brown colours. Very rarely was also discovered bicolor moldavites, probably due to the combination of two distinct moltens before impact. Chemically, it is silicate glass, except for SiO2, which is 70-80 % represented in moltens, we can find Al2O3 in the composition. MgO, CaO or Fe oxides. The hardness varies between 6 and 7 of Mohs scale
Macroscopically, they have a very peculiar appearance and they are mostly in the shape of balls, sticks, droplets, also rarely for heart or hedgehog shapes (Fig. 5). A great interest is the sculpture, which occurs mainly on the Moldavites from southern Bohemia. This is the name of the surface of the individual samples, which has been disturbed by the acids contained in the soils. These acids then stick to the surface of the Moldavite over time, resulting in a certain wrinkling of the surface, which is quite valued. Moldavites also contain a number of inclusions, which take the form of closed-gas bubbles. Because the Moldavite is chemically very close to the glass, it is sometimes difficult to distinguish the cutted Moldavite from the cutted green glass.
Fig. 5: Rare hedgehog Moldavite form; Taken over: http://observatory.cz/static/vystavy/vltaviny/4-vltaviny.php
The sand pit, which we visited as part of our excursion, belongs geologically to the South Bohemian basins, where sedimentation began during the Cretaceous period and continued until the Tertiary. The basins are composed primarily of fluvial and lake sediments. In the visited sand pit we find Moldavites in the Domanín formation, in the Korosec series, in sands to gravel with clay inserts. Moldavites are a rare mineral, and a lot of people want them to make money. In most cases, they dig even a few meters deep pits (Fig. 6) to get into the layers that contain the Moldavites. Unfortunately, this intervention often destroys nature, natural root systems and endangers animal safety. This problem has been solved for several years and is likely to be solved by extracting all layers with Moldavite findings (except fields) followed by rehabilitation to the original natural conditions.
Fig. 6: Consequences of illegal mining; Photo by Jan Šulc
The whole excursion was a great success and we would like to thank the owner of the sand pit Ing. Viktor Weiss, who allowed us to enter the normally inaccessible area. We would also like to thank Mgr. Miloš Faltus, Ph.D., who gave us a professional lecture and last but not least, we would like to thank the entire SGA for our long-standing support and favor
Baier, J. (2009). Zur Herkunft und Bedeutung der Ries-Auswurfprodukte für den Impakt-Mechanismus. Jahresberichte und Mitteilungen des Oberrheinischen Geologischen Vereins, 9-29.
Baier, J. (2007). Die Auswurfprodukte des Ries-Impakts, Deutschland. Verlag Documenta Naturae.
Vand, V. (2009). O původu tektitů a vltavínů. Pokroky matematiky, fyziky a astronomie, 54(1), 23-32.
Řanda, Z., Mizera, J., Frána, J., & Kučera, J. (2008). Geochemical characterization of moldavites from a new locality, the Cheb Basin, Czech Republic. Meteoritics & Planetary Science, 43(3), 461-477.
Skála, R., Strnad, L., McCammon, C., & Čada, M. (2009). Moldavites from the Cheb Basin, Czech Republic. Geochimica et Cosmochimica Acta, 73(4), 1145-1179.
Comments Off on Field trip: Heritage stones of central part of Bohemian massif
This field trip was focused on visits of heritage stone deposits and it’s following processing.
During trip were visited quarries Přibylov (siltstones), Škrovád (sandstones), Prachovice (limestones,
marble, schists), also historical town Chrudim and its historical heritage stone sights and Lipnice nad
Sázavou town with visit of local sculptor and his work.
Leader: RNDr. Barbora Dudíková Schulmannová (Czech Geological Survey)
Comments Off on Traditional autumn field trip: Various metal, precious stone and heritage stone deposits of central and east Slovakia
1 st day: Dřínová quarry (duplex structure with nice samples of barites in limestones) and visit of mineralogical exposition in gallery Patriot in Tišnov. 2 nd day: Špania Dolina area in the central Slovakia (heap with celestines samples, Piesky locality with azurite samples and Richtarova loc. which is type locality for deviline) and visit of Dobšiná with ongoing research of Ni and Co deposits. 3 rd day: Gretla (spekularite and goethite deposit), Novoveska huta (heap Bartolomejka with tyrolite and other Cu secondary minerals) and mine Josef close to Dubnik, where is gem quality opal deposit. 4 th day: open pit mine Fintice close to Přerov (andesites with zeolite samples) Leader: Bc. Jakub Mysliveček (Czech Geological Survey)
During
19–20th
of May 2018 the SGA Student Chapter Prague organized the Gold Short
Course led by Prof. David I. Groves from the Centre for Exploration
Targeting, UWA, Australia. There was an icebreaker organised in the
Chlupáč’s Museum of Earth History in the Faculty of Science, which
was a great opportunity to experience this newly established
exposition with a glass of wine (Fig. 1). This event also took place
in the Faculty of Science, Charles University, Prague, Czech
Republic, where 77 participants from 13 countries and 6 SGA Student
Chapters came to attend lectures by Prof. Groves (Fig. 2, 3).
David
I. Groves is an Emeritus Professor at the University of Western
Australia (UWA). He is considered to be a world leader in the
research of ore deposits, particularly orogenic gold and IOCG
deposits, and global metallogeny. On the UWA, he helped to establish
the Centre for Exploration Targeting. He has authored
and/or co-authored more than 500 publications, mainly in the fields
of Archean evolution, komatiite-associated Ni-Cu deposits, orogenic
gold deposits, the role of lithosphere in global metallogeny, and
prospection mapping. He was elected President of the SGA, SEG and the
Geological Society of Australia, and for his outstanding achievements
during his career, he received both the SGA Newmont Gold Medal and
the SEG Penrose Gold Medal.
Each
day of the short course was focused on different topics within 4
lectures:
1st
day – Orogenic gold deposits:
1st
lecture: Introduction to orogenic gold
2nd
lecture: The crustal continuum and genetic models for orogenic gold
3rd
lecture: Critical factors controlling the formation of orogenic gold
4th
lecture: Exploration targeting for orogenic gold
2nd
day – Gold deposits on craton margins:
5th
lecture: Introduction to intrusion-related gold deposits (IRGDs)
6th
lecture: Nature of hybrid magmas and genesis of IRGDs
7th
lecture: Carlin-type gold deposits of Nevada and China
8th
lecture: Iron-oxide copper-gold deposits: nature and genesis
SGA
Student Chapter Prague is grateful and would like to thank Prof.
Groves for leading this short course and we would also like to thank
all our sponsors who supported us during the organization of this
event. Especially the SGA Educational Fund for the financial support
and the bakery Kabát, butchery Göergl, company Vitana and brewery
Staropramen for their excellent catering (Fig. 4).
Fig.
1: Ice-breaker visits of Chlupáč’s Museum of Earth History. Photo
by V. Santolík.
Fig.
2: Ongoing lecture by Prof. Groves. Photo by V. Santolík.
Fig.
3: Group photo of all participants by V. Santolík.
Fig.
4: Food provider Michal Čurda with refreshments and sponsors logo.
Photo by M. Tuhý.
Field
trip
The
post-course field trip took place during 21–23rd
of May 2018 to various deposits in the Bohemian Massif. On this trip
participated 14 SGA members, besides the Prague Chapter’s members
also the Baltic, Black Forest and Moroccan members + SGA members
without chapter.
1st
day
We
visited the Jílové gold district, which is characterized by three
main types of gold-bearing ore bodies differing in morphology: ore
veins representing the main type of mineralization mined in the past,
gold-bearing stockworks representing the type of mineralization of
greatest economic importance and stockworks of irregular shapes
passing into impregnation zones which are developed at the eastern
margin of the albite granite body between the Šlojíř and Kocoury
vein zones, forming the Klobásy ore zone in the southern part of the
Jílové district (Pepř mine). Firstly, we have visited two
historical galeries, St. A. Paduán (Fig. 5) and St. Josef gallery,
where it was possible to see historical styles of mining. Afterwards
we moved to the more recent Pepř mine with Václav gallery which was
finished during the second half of 19th century when the underground
exploration of the southern part of the Jílové district occurred.
Since 2012, this mine is under control of the Montanika society, who
is removing the obstacles and taking care of the mine and to whom we
would like to thank for an excellent visit, especially to the leader
of this mine-tour Dr. Pavel Škácha (Fig. 6).
Fig.
5: Historical gallery St. A. Paduán. Photo by L. Kyrc.
Fig.
6: Introduction speech by Dr. Škácha in front of Václav gallery.
Photo by L. Kyrc.
2nd
day
We
moved to the Krušné hory Mts. on the NW part of the Czech Republic
and, in the morning, we visited the historical town Jáchymov, which
is an old well-known mining district operating since 1511. In the
beginning, silver was mined in secondary cementation zones and in
1519, the first Šlik’s Thaler was minted. This name was then
transformed into the currency dollar. During the 16th
century, 350 tons of silver were obtained. In the 19th
century, this was the deepest mine in the world (665 m). After the
discovery of uranium,local mines produced high quantities of this
element and it was used mainly for glass and ceramics coloring. After
the discovery of radium and upcoming radium rush, the first radium
spa was established (1906) which is still in operation. Because of
this, Svornost mine, is still operating and pumping the radioactive
waters used for healing treatments (Fig. 7). Jáchymov ore district
is a typical example of the five-element formation Ag-Co-Ni-Bi-As and
U-formation formed as a medium temperate vein hydrothermal deposit in
the Czech part of the Krušné hory Mts. (Erzgebirge). Up to 430
minerals, both primary and supergene, have been discovered and
described in Jáchymov up to now (latest figure counted by J. Plášil
in February 2011). After the mine tour, we also visited a local
museum with a beautiful mineralogical collection from this area and
with historical insight to the Jáchymov town.
The
next stop was the historical mine Mauritius (Fig. 9) located near the
town Horní Blatná, which has been an important mining center for
the past several centuries, mainly for tin, and secondly for silver,
iron, cobalt and later manganese ores. The mine was closed in 1944
and today provides well preserved historical galleries mined from the
end of 16th century. The occurrences of tin ores are bound to the
biotitic granites of the Blatná massif that build the wider
neighborhood of the Blaten Hill. The granites are greisenized and
enriched with mica, tourmaline, quartz, chlorite and especially
cassiterite.
Close
to the borders with Germany, we visited a skarn deposit called Zlatý
Kopec, which is a lens-shaped body of diopside- and
diopside-actinolite skarn in a chlorite-sericite phyllites complex.
Ore minerals are cassiterite, sphalerite, chalcopyrite, and
magnetite, which we had the opportunity to collect on the heaps near
the gallery Johannes.
Fig.
7: Taking bath in warm radioactive spring Běhounek directly in
Svornost mine more than 500 m below the surface level. Photo by L.
Kyrc.
Fig.
8: Group photo in front of Svornost mine. Photo by L. Kyrc.
Fig.
9: Introduction talk in Mauritius mine. Photo by L. Kyrc.
3rd
day
On
the last day, we firstly visited an open-pit mine and processing of
gem-quality pyropes, which are famous under the name “Czech
garnet”. Czech garnet separating plant and the open-pit mine (Fig.
10), called Panské jámy, are situated close to the Podsedice
village in the České Středohoří area (Central Bohemian Uplands –
a neovolcanic field on the north of Czech Republic). There are
approved reserves with a garnet content of about 40 g/m3.
Garnets are mined easily by excavators from alluvial sediments, but
originally, garnets come from near volcanic spots (diatremes), whose
breccia filler contains blocks of serpentinized peridotite rich in
those garnets. After separating garnets with the proper size and
quality, they are sent for cutting and are used in the famous
jewellery made by the company Granát Turnov.
After
the garnets, we moved to the northern part of Krušné hory Mts.,
where we visited Krupka town surroundings in one of the youngest
mining districts in this area named Knöttel (Bohosudov) situated on
the east of Krupka area. The underground mining in this region,
started in the 18th
century. The deposit was formed in gneisses and was mainly exploited
for tin and molybdenum mineralization. We started our tour close to
the Barbora gallery, one of the molybdenum mine galleries exploited
during World War 2. Then, we stopped near Siebenschläfer, a modern
gallery with tin, copper and bismuth mineralization mined mainly for
cassiterite. Next stop was on an old heap with high contents of
native bismuth accompanied by chalcopyrite (Fig. 11). Another nearby
stop was the Zwickenpinge, an open-pit with small shafts and heap
with secondary copper mineralization and the first place of surface
mining of tin and copper ores originated in 13th
century. We also visited an open-pit above Prokop gallery, molybdenum
mine with quartz body and greisen vein with occurrences of
molybdenite, fluorite, topaz etc. The last stop was at the place
where the quartz vein called Lukáš surfaces and where it was
possible to find samples of green apatite crystals up to 1 cm,
tin-rich mica zinnwaldite and some fluorite crystals.
Finally, we would like to thank
all the leaders of the separate trips, especially to Dr. Pavel Škácha
from the Pepř mine in Jílové district and Dr. Jakub Plášil and
Dr. Viktor Goliáš for leading the trips to Svornost mine in
Jáchymov. Special thanks to the Svornost mine and company Granát
Turnov for allowing us to explore their mines and also to all the
sponsors mentioned above.
Fig.
10: Collecting of small gem-quality pyropes in the open-pit mine near
Podsedice village. System of cascades for cleaning processing waters.
Photo by J. Mysliveček.
Fig.
11: Collecting samples on the heap rich on native bismuth. Photo by
J. Mysliveček.
