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.

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

Report from the Gold Short Course 2018 (led by Prof. David. I. Groves) + post-course field trip in Bohemian Massif

Report from the Gold Short Course 2018 (led by Prof. David. I. Groves) + post-course field trip in Bohemian Massif

Jan Kulhánek, Marek Tuhý, Dominik Brém, Rafael Baieta

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

Photos album links:
Gold short-course: https://www.zonerama.com/SGA-Prague/Album/4347282
Post-Gold course Field trip: https://www.zonerama.com/SGA-Prague/583718

Short Course

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.

Field trip: SW part of Bohemian Massif- various deposit, cooperation with Baltic Student Chapter

Heritage Stone excursion to the Southwestern part of the Bohemian Massif

Eliška Bršlicová, Marek Tuhý, Rafael Baieta

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

Photos album link: https://www.zonerama.com/SGA-Prague/Album/3956885

The 2017 autumn field trip organized by SGA Student Chapter Prague took its participants to some world-famous locations, such as Komorní Hůrka, Kössain, Stříbro and Kašperské Hory. Here, we saw the heritage stones of the southwestern region of the Bohemian Massif.

Day 1

We started the day with a visit to the Tis u Blatna quarry (Fig. 1), which is currently mined by GRANIO s.r.o. The special type of granite at this site is locally called “Czech Labradorite” due to its bluish hues that are caused by quartz. Afterwards we visited localities near Horní Slavkov with Sn-W-Mo-Cu-rich quartz veins. First locality Huberův peň used to be mined for Sn and W. The erlan mineralization allows for fairly large crystals of cassiterite to be found alongside wolframite, green and violet apatite, chalcopyrite, topaz, molybdenite and violet fluorite. The second locality in this area, Vysoký kámen, is a greisen-type deposit, where green spheroid chalcosiderite-turquoise chain minerals were formed during decomposition. Finally, we visited the Štenská u Teplé quarry, the only locality in Czech Republic where trachyte is mined.

Fig. 1: Tis u Blatna quarry. Photo by M. Vopat.

Day 2

In the morning, we arrived to Komorní Hůrka (Fig. 2), one of the youngest volcanoes in the Czech Republic, with its age being estimated between 200 000 and 1 million years. Kormorní Hůrka is a stratovolcano, with interchanging eruptions of basaltic lava flows and pyroclastic deposition, both tuff and volcanic bombs can be found at this locality. Afterwards we moved on to Marktredwitz (Fig. 3) where the highway cuts through an assortment of redwitz, from granodioritic to gabbroitic. The next point of interest was Blue Granite in Pfalzbrunnen quarry outside of Kössain. The granite here is being mined for 100 years and is prized for its porphyric structure and fine quality.

Fig. 2: Goethe’s adit for research purposes at Komorní Hůrka. Photo by M. Vopat.

Fig. 3: Feldspars at Marktredwitz. Photo by M. Vopat.

Day 3

We visited Stříbro (Fig. 4), a famous Czech locality with Pb-Zn mineralization and a great history of mining. The first known document referring to the silver mines is from the 12th century. Silver was mined in this area throughout the Medieval ages, then around the 16th century, lead started being mainly mined. The veins contain multiple quartz generations along with galenite, sphalerite, pyrite with marcasite and occasionally chalcopyrite. Then, we moved to a uranium deposit Damětice. It used to be a small mining area. The upper part of the deposit is oxidized and its possible to find uranium micas such as uranocircite, autunite and torbernite while the lower deposit contain primary mineral uraninite. Later, we visited an old marble quarry in Nezdice na Šumavě. The marble in the lower part of the quarry has a beautiful sky-blue color and contains fine needles of wollastonite. We ended our day in Kašperské Hory, an area full of historical gold mines from the 10th and 14th century. The latest geological survey still shows deposits of gold with 5.6 ppm Au.

Fig. 4: Stříbro, heap from Pb-Zn mine. Photo by J. Mysliveček.

Day 4

We arrived early to Malenice (Fig.5), where we observed migmatite and paragneiss boulders containing almandines. Tetragonal trioctahedral and rhombic dodecahedral crystals can be found here or the combination of both. Than we explored the locality Sepekov and we found a group of hercynite spinel-rich rocks and varying content of phlogopite located on the contact of a gneiss-migmatite and tourmaline granite rock bodies. We ended our field trip in Krásná Hora nad Vltavou at an extensive mineralization of gold and antimonic veins stretching throughout the area. We searched around an old rock pile from the mine shaft Emilka consisting of red stained granite with antimony crystals and grains.

Fig. 5: Malenice, paragneiss containing almandines. Photo by D. Brém.

Field trip: Heritage stones of N part of Bohemian massif

Date: October 19-20, 2017

Program: First day we visited famous heritage stones deposits: Ruprechtice (typical granit deposit “Liberecká žula”) and Spa Bělohrad – quarry Javorka (nicely coloured sandstones). Then we moved to Hořice town, famous by its sculpture school, which we also visited. Here we joined the lecture about “How the statue is made” and also seen different processes and approaches of making statues. Besides the school we also visited a famous park and graveyard with many sculpture works (many times made by famous sculptors) from local school.

Leader: RNDr. Barbora Dudíková Schulmannová (Czech Geological Survey)

Attendance: 10 members of our Chapter

Gold Short Course 2018 (Prof. David I. Groves)

  We would like to thank you all for participation at two-day Gold Short Course by Prof. David I. Groves and we are looking forward seeing you again! Please find our online gallery with photos from short course and post-course field trip.

     

 

Link for downloading the presentation slides here (repaired)


We would like to invite you to a two-day Gold Short Course by Prof. David I. Growes from the Centre for Exploration Targeting, UWA, Australia. The course will take place on the 19th-20th May 2018 in the building of the Faculty of Science, Charles University in Prague, Albertov 6. The ice-breaker is planned for the evening of 18th May (Friday), start at 5 pm. Attendance on the short course is for free thanks to SGA Educational Fund, but the field trip is charged by 160 EUR for SGA members and 280 for non-members.

  For any question about the Gold Short Course please contact us on gold.course.prague@gmail.com. Registration form for Gold Short Course and information about our post-short course field trip please find in the links below.

Please send your registrations on the email above. (In case of not responding please try to contact us on our personal emails).

 

Schedule of Gold Short Course

Saturday

OROGENIC GOLD DEPOSITS

Before 9 am: morning coffee

9:00- 1st lecture: Introduction to orogenic gold

10:35- coffee break

10:55- 2nd lecture: The crustal continuum and genetic models for orogenic gold

12:30- lunch time

14:30- 3rd lecture: Critical factors controlling the formation of orogenic gold

16:05- coffee break

16:25- 4th lecture: Exploration targeting for orogenic gold

18:00- expected end of the Saturday program

 

Sunday

GOLD DEPOSITS ON CRATON MARGINS

Before 9 am: morning coffee

9:00- 5th lecture: Introduction to intrusion-related gold deposits (IRGDs)

10:35- coffee break

10:55- 6th lecture: Nature of hybrid magmas and genesis of IRGDs

12:30- lunch time

14:30- 7th lecture: Carlin-type gold deposits of Nevada and China

16:05- coffee break

16:25- 8th lecture: Iron-oxide copper-gold deposits: nature and genesis

18:00- expected end of the Sunday program

*Cancelling with refund is possible only until two weeks before each trip.
**Organizers reserve the right to cancel a field trip for lack of participants.
***Besides Icebreaker party and coffee breaks, food and drink is not provided by the organizers of the Shortcourse.

Guide: Transport, dining, etc.

Registration form for the Gold Short Course and field trip

Informations about our post-Short Course field trip


Articles about the issue to see beforehand- Gold Short Course files:

Groves-et-al.-GSF-2018
Groves2010EG IOCG PAPER
GSF Giant Gold Provinces
Muntean_et_al_Carlin_Genetic_Model-2011
Lithos Paper
Hronsky et al. Paper MIDE-S-11-00118[1]
GSF-D-17-00399. Jiaodong. pdf
GSF Kalgoorlie Vielreicher

Field trip to the central part of Krušné hory Mts. (Erzgebirge)

This two day field trip took place from 3th to 4th of June 2017 and was concipated to visit mainly Fe, Mn and fluorite deposits in the central part of Krušné hory Mts. (Erzgebirge) with some additional stops on other deposits.

First day:

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We started the excursion in town Horní Blatná. Here we visited vein of Marie Terezie and heap of Concordia adit . Minerals occurring there were mostly Mn ore – pyroluzite. We found also quartz in small crystals up to 3 mm. Then we moved to „Ametystová Halže“ near Horní Halže village. This site is old mining part of Měděnec district and there is a large number of surface exposure of old mining activity. We found mostly amethyst and quartz crystals, ordinarily in clusters up to 7 cm and the primary Fe ores like limonite and pyrite.

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After first part of the excursion we moved to rock formation called „Sphings“ near town Měděnec formed by very high pressure deformed „eyes-schist“ from Variscian orogeny processes.

DSCN4446From this place we could see landscape of Doupovské hory volcanic centre. Our another stop was at Mědník hill near town Měděnec. This small hill is the skarn body preparated by erosion in Quaternary and one of the most mined Fe and Cu deposit in early modern age. We ascended to the top of the hill around old skarn heaps and there was lecture about local mining from medieval to the end of 20th century.

Second day:

DSCN4502The weather condition did not allow us to see all three fluorite deposits in Krušné hory Mts. according to former plan, but only Hradiště fluorite deposit near Kadaň town and Kláštěrec nad Ohří town. This small deposit was mined for barite, fluorite and hematite. We found only fluorite and hematite samples. After that we moved to The Chateau at Klášterec nad Ohří town, where was also an exhibition of local minerals. We saw very nice samples of polished agates from Horní Halže village, Černý Potok vil., Ciboušov vil. and other sites.

 

After that we visited local spa area and we drank local hydrothermal water from the spring. P1270149This hydrothermal energy is caused by volcanic activity bound on Ohře rift and was formed mostly in Tertiary. Then we moved to quick visit of Ahníkov (former vil.) – site with minerals of weathering of laterites. We found specific minerals like white and purple chalcedone, green chryzotile and small crystals of quartz. After that we moved to our last site which was Lehnschafter adit in Mikulov town. Mikulov was mined mostly for Ag ores like Ag-rich galenite.

 

Eight Chapter members paticipated on this excurstion led by Bc. Jakub Mysliveček.

For more photos please visit this link.

Field trip to the historical mining in Kutná hora and its surroundings

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First day:

Visiting of adit St. Jiří in Oselské district – Medieval adit St. Jiří is a part of the mining-historical exhibition of the Czech Museum of Silver. This adit was discovered in 1967 during a hydrogeological survey and the length of its accessible part is about 280 metres.
Quarry Práchovna – A new outdoor geological exposition was opened in August 2014 in the former quarry Práchovna. In this exposition are used a blocks of rocks from Kutná Hora area, Kolín and Chrudim with thematically structured panels.

P1260547The slag heaps – were deposited in the immediate vicinity of the silver smelter. The ironworks in the Vrchlice Valley were in operation from the 15th century until the end of the 18th century. This despite of the partialy flattened heaps, containing an estimated 400,000 tons of slag, are witnesses of the vast range of medieval metallurgical activity in the area.
The St. Antonín Paduánský – is one of the most important mineralogical sites of the Kutná Hora region. The work followed a vein with a high content of antimony and silver ores. In the adit and in the dump we can get to know not only with typical veined minerals, but also with some luck we find rare silver ores. Our findings: berthierite, kutnohorite, pyrite, cave pearls.
The site of the former RD Kutná Hora establishment – here is the Turkaňk mine, which draws the mined water treated in the built-up cleaner for user quality. A large basin in the southern part of the Turkaňk zone was created by the mines collapse in 1969. In the eastern wall of the basin is a gallery of an old mine about 100 m long. This old gallery belongs to the oldest phase of Kutná Hora mining.

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Old heaps after mining of ores in the village of Kaňk – This dumps are an interesting occurrence of rare arsenic minerals. For the last two years, heaps have been involved in many pitfalls because they have been exposed to erosion or by targeting of the collectors. Hopefully, due to the timely intervention of the experts which was made, there will be no complete disposal of the heaps, as was previously thought. Our Findings: bukovskite, kaňkite.

Second day:

P1260684Malešov – a magnetite rich rock deposit opened by deep mines. Our findings: magnetite, garnet, pyroxene, amphibole, prehnite, calcite, epidote.
Markovice – active amphibolite quarry near Čáslav. Known occurrences of alpine type minerals. Our Findings: prehnite, titanite, albite, calcite.
Kožlí near Ledeč nad Sázavou – a small fluorite deposit with a high content of quartz. Our findings: fluorite, quartz.

Fourteen Chapter members participated on this excursion led by Mgr. Jan Bubal.
For more photos please visit this link.

Field trip: Historical mining of Pb, Zn and Ag deposits in the Kutná Hora ore district

Date: June 3-4, 2017

Program: This two-day field trip was concipated to visit mainly Fe, Mn and fluorite deposits in the central part of Krušné hory Mts. (Erzgebirge) with some additional stops on other deposits.

Leader: Bc. Jakub Mysliveček

Attendance: 8 members of our Student Chapter