Josef Gallery

About the Josef Gallery

The Underground Educational Facility is located 50km south of Prague, near to the Slapy dam, between the villages of Čelina and Smilovice. It is constructed in an abandoned mine, known as „Josef gallery“. Among all the sites considered, Josef was found to best fit to the following criteria:

• location close to Prague 
• financial feasibility (purchase price, reconstruction and operating costs) 
• varied geological conditions (occurrence of non-monotonous geological formations)
• the site’s potential for future expansion 

• a potential to construct modern support facilities
  

The Josef exploration gallery runs in a NNE direction across the Mokrsko hill rock massif. The total length of the main drift is 1836m, with a cross-section of 14–16m². The overlying rock thickness is 90–110m. Two parallel tunnels lead from the entrance portals, each having a length of 80m and a cross-section of 40m². The main exploration gallery is connected to various exploration workings by numerous insets, which follow ore formations and provide access to two further levels. The total length of the galleries is approx. 9km; 90 % of the breakings are not fitted with linings. The end of the main gallery is connected to the ground surface by means of an unsupported 110m vent.

The Josef gallery is located in an area of Psí hory auriferous deposits. The geological structure conssist of volcanic rock (basalts, andesites, rhyolites), sedimentary rock (hornfels) and their combinations (tuffs, tuffites), characterised by younger intrusive rock types (granodiorites, albitic granites).

Technical data:

Scheme of the Josef Gallery

Geology In the Vicinity of the Gallery

The Josef gallery was excavated as part of the exploration of the Psí hory gold-bearing district which is located mainly in the proterozoic Jílovské belt, in rock of more than 600 million years old. These rocks were subsequently penetrated by Central Bohemian Pluton granitoid rocks during the Variscan orogenesis.

The Jílovské formation consists of a 1-6 km wide and up to 70km long belt of volcanic and subvolcanic rocks stretching to the south-west of Jílové u Prahy containing other gold mining areas in addition to Psí hory (Jílové u Prahy, Štěchovice-Slapy, Smolotely-Horní Líšnice). Historically, the most important mining activity was concentrated in the vicinity of Jílové u Prahy.

In the Psí hory area, the Jílovské belt consists of volcanic rocks of both basic and acidic composition (basalts, andesites, dacites and rhyolites) in the central area with subvolcanic plagiogranites at its eastern edge and gold-bearing acidic to intermediate tuffs.

The overburden consists of a volcanic-sedimentary formation consisting mostly of tuffs and tuffitic shales. To the west, the Psí hory mining district extends to the margin of the biotitic-amphibolic granodiorite of the Central Bohemian Pluton.

Towards the end of the 20^th century the Psí hory district was systematically explored in connection with the potential revival of gold mining. There are two gold-bearing deposits in the area – the Čelina deposit, mined as early as in the middle ages, and the Mokrsko deposit. The Čelina deposit and the eastern Mokrsko ore-zone are situated in the tuffs and volcanites of the Jílovské belt. Most of the western Mokrsko ore zone lies in the granodiorite of the Central Bohemian Pluton.

The gold reserves in this area are some of the richest in Europe. According to recent estimates, local deposits contain up to 130t of the precious metal. The gold mineralization is concentrated in quartz veins and veinlets and is mostly very fine grained. The average gold content in the rock is no higher than 2 g/t, which explains why the Mokrsko deposit escaped the notice of medieval miners; its potential was only fully recognised as late as in the nineteen eighties.

At the end of the last century, the revival of gold mining in this area was seriously considered; however, the highest concentrations of gold occur at depths of up to 300m meaning that the gold would have to have been exploited by open-pit mining. Moreover, the separation of the gold would have required the use of the environmentally unfriendly cyanide process. Consequently, commercial gold exploitation is not currently envisaged and is not likely in the near future.

References:

Morávek, P. (1992): Zlato v Českém masivu. Nakladatelství ČGÚ, Praha, 248 p.

Morávek, P. - Litochleb, J. (2002): Jílovské zlaté doly. Regionální muzeum v Jílovém u Prahy, 187 p.

History of the Gallery

The Josef Gallery

The Josef Gallery underground complex was constructed during the large-scale geological exploration of the Čelina and Mokrsko gold bearing deposits in the nineteen eighties. The excavation of the gallery commenced in 1981 and subsequently served exclusively for exploration purposes (see below). In the mid 1990s exploration of the area ceased and the gallery was closed whereupon it began to deteriorate rapidly leading to the plugging of both the access portals in 2000.

The Faculty of Civil Engineering, CTU realised the potential that the by now somewhat dilapidated Josef complex provided for educational and research use and in 2005 an agreement on the use of the gallery for such purposes was signed between the faculty and the Ministry of the Environment which owned the complex. Renovation work, carried out by Metrostav Ltd at its own expense, commenced almost immediately. In February 2007 Metrostav handed the complex over to the faculty. Currently 600 metres of underground galleries is accessible. Work aimed at improving access to the rest of the underground complex continues and a project for the construction of a surface support facility is currently in the preparation stage.

History of the Josef Gallery and the Tradition of Gold Mining in the Psí hory (Dog hills)

The Josef Gallery was excavated in the nineteen eighties as part of the exploration of a traditional gold-bearing district known, as early as in the Middle Ages, as the Psí hory. The Psí hory district is situated approximately 7km south-east of the town of Nový Knín formerly one of the most important mining centers in the Czech Kingdom.

In the past the Nový Knín district became famous for its large number of gold deposits. Even though the local mines never earned the same reputation as those in nearby Jílové u Prahy, the Nový Knín area can boast a rich mining history.

In addition to the Psí hory, gold was excavated in three other districts in the vicinity of Nový Knín: the Nový Knín district itself (the area between Nový Knín, Krámy and Malá Lečice), the Kozí Hory district (situated between the villages of Kozí Hory and Borotice south-west of Nový Knín) and the Libčice district (south of Nový Knín between Libčice and Dražetice) which was considered the most important of the four and where gold was mined intermittently from the Middle Ages to the first half of the 20^th century.

The Psí Hory district is the only one of the four which is made up of rocks of the so-called Jílovské belt, named after the town of Jílové u Prahy. The gold mined in the vicinity of Jílové played an important role in the medieval history of the country. It was used for the first time in Central Europe by king John of Luxembourg as the principal raw material for the minting of ducats. Thereafter, the mining of gold continued near Jílové for several centuries up to the termination of gold mining in the area in 1968.

The commencement of gold mining

There are very few written records remaining concerning the history of gold mining in the Psí Hory. However, in many places what remains of old mines can still be seen today.

In the Czech Lands gold exploitation reached its first peak during the Celtic period, particularly in the 2^nd and 1^st centuries B.C. The Celts obtained most of their gold by the panning of surface deposits. The existence of former panning locations along the Čelina stream and in the alluvial sediments of the Vltava river near Smilovice near to the ruins of the Celtic settlement of Hrazany would tend to suggest that Celtic miners were active in the Psí Hory.

13^th and 14^th centuries – mining reaches its peak

After the exodus of the Celts, local gold deposits were not excavated for several centuries. The principal gold mining period in the Psí Hory came in the middle ages. Hard rock mining probably began at the turn of the 13^th and 14^th centuries. During the 14^th century gold exploitation in the Psí Hory reached its peak at which time gold was mined from quartz veins reached via cross drifts and galleries located throughout the district especially in the vicinity of Čelina. Underground workings were, on average, 20m long with a maximum depth of 60m below the surface. A blacksmith’s forge used for the production of mining tools would typically be situated close to the larger mining shafts. Several ore-crushing mills were situated along the Čelina stream.

Medieval miners used very simple equipment. In the underground areas they used lamps filled with tallow and mined the ore with iron hammers and angular mallets. The hammer would be held in the left hand and placed on the rock whereupon the mallet was used to hit the hammer thus breaking off pieces of the gold-bearing quartz. The hammers wore out fast; it is estimated that one miner used more than twenty hammers during a typical shift.

The ore was then transported to the ore mills where it was crushed and milled; the gold was separated from the ore by the process of amalgamation.

Mining began to decline at the turn of the 14^th and 15^th centuries due to increasing costs, the technical difficulties of mining at increasing depths, the exhaustion of the accessible sections of the ore veins and political change. Consequently, the mining of gold ceased for a period of several decades.

The revival of mining in the 16^th century

At the turn of the 16^th and 17^th centuries mining activity recommenced; however, this second period of gold exploitation lasted only for a short time and is considered less important than the previous phase. According to contemporary accounts the waste dumps of the former Lodice mine “were used for further mining” in 1536. Such dumps were recorded up to 1550 in the Nový Knín Mining Office mining book. The ore mills along the Čelina stream are mentioned in the Czech Kingdom land registers of 1548. The records are, however, written in the past tense which would tend to suggest that the mills were no longer in use at that time. It can be assumed therefore that mining activities ceased in the mid 16^th century.

It is interesting that unlike other districts in which gold mining and exploration continued at later times, the Psí hory escaped the further notice and interest of gold miners until the late 20^th century.

Most remaining records of mining activity in the area refer to old workings concentrated in the vicinity of the village of Čelina; the most extensive old mining workings are situated approximately 1.5km to the east of Čelina in the western part of the Koňský hill. Practically no attention was paid to quartz veins near the village of Mokrsko as they contained very fine-grained gold which was difficult to detect.

Archeological research carried out in the mid 1980s contributed significantly towards improving our knowledge of the mining history of the Psí hory bringing to light a range of interesting artifacts including ore milling stones, the remains of a medieval blacksmith’s shop, iron mining tools and ceramic mining lamps.

Unfortunately it is not known precisely how much gold was produced during the two main periods of mining in the Psí hory. However, it is known that a total of 4t of gold was mined in the Nový Knín district. (Just for comparison – the total production of Jílové mines was estimated at approximately 10t of gold and the total production of gold in the Czech lands is estimated at 100 t of this precious metal.)

Geological exploration of the Psí hory during the 20^th century

No mining or exploration was carried out in the Psí hory district from the 16^th century until towards the end of the 20^th century. In 1977-1980 the Jílovské belt rocks were subjected to large-scale regional exploration during which potentially important gold reserves were discovered in the Psí hory. Further detailed exploration followed in the 1980s which included geological mapping, geophysical research, the detailed geochemical research of soils, drilling to depths of between 300m and 600m and underground drilling and mining research in the newly excavated Josef Gallery.

The following review documents the thoroughness of the research:

• 103 core holes were bored from the surface with a total length of 23 378m
• 127 underground core holes were excavated with a total length of 13 137m
• the Josef Gallery was excavated and included:
•           a main drift crossing all the deposits – length 1835m
•           drifts crossing particular deposits – total length: 6018m
•           3 ventilation shafts – total length 330m
• 9 818 soil samples and over 25 000 rock samples were collected and analyzed.

The exploration resulted in a detailed evaluation of existing gold reserves in known deposits, an estimate of the amount of gold mined in the past, and, interestingly, the discovery of a previously unknown deposit, named Mokrsko-West. It is estimated that Mokrsko-West contains 75 tonnes of exploitable reserves which makes it one of the richest gold deposits in Europe. The total gold reserves of the Psí hory district are estimated at approximately 130 tonnes which is more than the total amount of gold produced in the Czech lands to date.

The experimental underground exploitation of the Čelina deposit took place as part of the exploration process between 1989 and 1991. Over the three year period, 19 500 t of rock was removed and processed at the preparation plant in Příbram. The rock produced a total of 21kg of gold.

Notwithstanding, commercial exploitation has never been seriously considered since gold would have to be mined using open-pit mining techniques which is considered to be environmentally unacceptable. In the mid 1990s several foreign companies considered gold mining in this location but abandoned the idea following the vociferous protests of local people and various environmental organisations.