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 Mráček
Fig. 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).

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.”

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.

Moldavites of South Bohemia

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 Šulc
Fig. 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.

Prague SGA Student Chapter visiting Columbia-Bogotá SGA Student Chapter: Mineral deposits of Columbia

Štěpán Jaroměřský, Ivan Mateo Espinel Pachón, Jan Hofmann, Milton A. Santos

1SGA Student Chapter Prague, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic; jaromers@natur.cuni.cz

Photo of the whole group of participating members

As every year, Prague Chapter participates in several fieldtrips with friendly chapters. This year, we managed to negotiate several daily fieldtrips with the SGA Student Chapter Columbia-Bogotá, which should have focused on emerald and gold deposits. The main target was to visit the world famous emerald deposit near the town of Muzo. However, the whole program was charged and very well prepared by the Colombia-Bogotá Chapter. The Prague chapter was represented by 10 members and the field trip lasted from March 19 to 25.

1st day:

On the first day we visited a sedimentary-exhaliative deposit (SedEx) near Chiquinquirá – Boyaca. Sedex are ore deposits formed by a release of ore-bearing hydrothermal fluids. Subsequently, they must be released into a water reservoir, resulting in the precipitation of stratiform ore. SedEx deposits are the most important sources of lead, zinc and barite. These ores are processed for tungsten, copper, silver, gold and bismuth.

This deposit is located high in the mountains of northern side of central Colombia. 10-year-old exploration galleries designated for researching copper in the past surround the site. There are abundantly chalky sediments, in which there are minerals of copper such as chalcopyrite. We also found some beautiful examples of barite crystals. It is a fairly extensive site, but because of the steep slope and dense fog, we stayed on the upper parts of this deposit. It was a nice introduction to Colombian geology and nature.

2nd day:

On the second day, our emerald trip started in Las Pavas area. We had accommodation in the town of Muzo, from where a very narrow path led through the local mountains. Muzo itself is well known for its emerald deposits.

Emeralds are usually found in calcite-dolomitic veins containing pyrite, ankerite, albite and quartz. These veins are the product of hydro-thermal fluids that disrupt the rock massif and the interactions of the metasomatic fluid with subsequent deposition in the breaks formed by these calcite-dolomitic veins. It is likely that metasomatic fluids come from shale formations near Muzo, which are probably the source of vanadium, which is the cause of the unique color of local emeralds.

Firstly, we headed to the Rio Magdalena where we could find some samples in the river or meander scrolls. Only one member of our chapter was lucky enough to find a small sample in the shale. We even investigated one closed mine which might be reopened in the near future.

Fine emeralds crystals from Muzo. Photo by E. Vrňatová

3rd day:

On the third day, we had a scheduled visit to El Líbano Tolima, the El Porvenir gold mine, orogenic and epithermal gold deposit. This mine is processing sulphide ores like pyrit, containing relatively large amounts of gold (up to 1000 ppm). The grains of gold in the bearing are mainly included in sulphides and silicates. The mineralization of gold in the bearing is probably caused by the penetration of porphyres into the Paleozoic slate on the eastern wing of Colombian Andes. It is believed that the mineralization of gold occurred in three early phases of intrusion, which are accompanied by a number of sodo-calcical changes and the late phase of penetration of porphyres. The samples contained high quartz and chalcopyrite content.

We travelled to the mine a long way on a car’s hull. Then we went through the inspection, which was waiting for us in front of mine. The whole mine is active and so we could only be there in the pause period. The whole visit was fantastic and very engaging. At the end, everyone could take only one sample of the size of a fist.

One of the eight entrace to the El Porvenir gold mine

4th day:

On the fourth day, we visited the Cu-skarn Payandé deposit with garnets.

The post-Triasic plutonic rocks, known as the Payande Stock, grow on the eastern edge of Colombian central Cordillery near San Luis-Tolima. The quarry could not be reached directly by our bus, so we had to stretched our legs. At least we were accompanied by a car that eased us from our backpacks and hammers. The road was not difficult, except from the ford across the river, where we had to take off our shoes and wade.

The reason why we drove there were skarn outcrops, where the great and beautiful crystals of andradite are located. Regarding the other minerals, hematite, azurite, quartz, calcite, chlorite, magnetite and sphalerite are also found here. Petrology and mineralogy is very interesting in this deposit, as there are signs of a passage of hydrothermal fluids and changing contacts with individual minerals. We saw the beautiful mineralization of the copper. There are also several zones to see. The first zone corresponds to the tonalites, the second to endoskarns and the third to exoskarns. There is also a prograde zone containing garnets and pyroxenes. In the retrograde zone, where iron oxides, iron sulphates and copper are found. This was our last locality in terrain.

5th day:

On the fifth day we were back in Bogóta and we had a planned tour of the geological section at the Universidad Nacional de Colombia. We went through some local classrooms and looked at a few samples from the local collections. We also examined a few rocks which we saw during the fieldtrip under a microscope and finally we listened to short presentations from Prague Chapter and Bogota Chapter. After exploring the area, we went to the city to taste a bit of all possible and impossible fruits on the world-famous market Plaza de Paloquemao. Then we moved to the Gold Museum in Bogota and the largest Emerald museum in the world. Unfortunately, this day the Emerald Museum was closed in, so we had to visited another day.

Finally, we would like to thank all the leaders of this fieldtrip, especially Ivan Mateo Espinel Pachón and all the SGA Student Chapter Columbia-Bogotá members for an amazing organization and for ensuring everything needed for the success of fieldtrip. In general, I think that the cooperation between Chapters is the best form of studying. Also I would like to express great thanks to the whole SGA, as it would not be organized without their support and many thanks to all our sponsors, such as Vitana or Severočeská doly.

I think that this fieldtrip to Columbia strengthened the connection between our SGA student chapters and we hope that despite the distance between Prague and Colombia we will continue to collaborate and exchange experiences.

Tasting of Colombian fruit delicacies by J. Bašus

17th Freiberg short course in economic geology 1.-4.12. 2019

Každoroční Short Course ložiskové geologie ve Freibergu. Letošní program na téma: Iron and Manganese Ore deposits.

Mezi dalším programem se můžete těšit na uvítací ice-breaker party v ložiskových sbírkách TU Bergakademie Freiberg, možnost navštívit výstavu Terra Mineralia a užít si sváteční atmosféru na vánočních trzích.

https://tu-freiberg.de/fakult3/min/econgeology/short-courses
Bližší info a registrace dle pokynů v emailu.

SGA Chapter Prague: Oncoming Colombia field trip

Prague Chapter SGA most anticipated event of 2019 is undoubtedly journey to Colombia. Members of our chapter are preparing geological field trip in cooperation with SGA Chapter from Bogota.

Our members have the unique opportunity to visit Colombian gold deposits and exclusive emerald mine of MUZU!

Do not miss a chance of your lifetime to visit rich deposits of beautiful Colombia and getting to know more SGA members around the world!

For more information stay updated with our newsletter.
Your SGA team



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)

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)

photo by Ľubomír Kyrc

photo by Ľubomír Kyrc