Prepared by: Ing. Martin Šefrna
Investor supervision: Bc. Jiří Loskot, Czech-Bavarian Geopark
Investor representative: Ing. Michael Rund, Director of the Sokolov Museum
Prepared in November 2023
Title page of the final report
TECHNICAL REPORT
1. Introductory data
2. Mining and geological conditions
3. Mining and technical and archaeological survey ODD-K3
4. Mining and technical and archaeological survey SDD III
5. Conclusions, recommendations
GRAPHIC ANNEXES
P1 Overview of the Jeroným Mine
P2 Documentation of the ODD-K3 Survey
P3 Archaeological Survey ODD-K3
P4 Documentation of the SDD III Survey
P5 Archaeological Survey SDD III
1. Introduction
The subject of the submitted report is a technical description of the exploration work within the framework of the mining-technical and archaeological exploration of the Jeroným mine in the SDD III and ODD sections of the KZ chamber. The exploration work was triggered by the remedial work carried out in 2023 with the intention of continuing the project "Repair of damage at the Jeroným mine".
Prospecting and exploration work were carried out in order to determine the mining-technical conditions and verify them on site. Along with the excavation work in the SDD and ODD areas of interest, an archaeological survey was carried out in the form of documentation, collection and rescue of archaeological finds.
2. Mining - geological conditions
NKP Jeroným mine is located 6 km from the town of Krásno in the direction of Sokolov. Mining works for the purpose of mining tin ores were excavated in the 16th-18th centuries in the endocontact of the Ore Mountains granites of the Krudum massif, in its southern part at the contact with the overlying pararules. The mining works are formed by excavated chambers connected by corridors excavated in biotite granite at a deposit inclination of 20-45° to the south. They are connected to the surface by collapses of excavated chambers or shafts and newly restored shafts. The thickness of the overlying rock is 2.0 m at the deposit outcrop, at the level of the drainage adit up to 50 m. Mineralized zones in granites (greisens) form several parallel positions in the contact zone, which were the subject of exploitation and predetermined the method of deposit development, i.e. irregular chamber mining with interchamber pillars of critical parameters left. In addition to mining works, the mine also includes exploratory mine works in the form of discovery shafts and exploratory galleries of an economical profile. Drainage galleries are a very important part of the mine. One of them is the well-known and already reconstructed Jeroným drainage gallery, driven in a southerly direction with a length of approximately 420m, which drains mine water from the ODD complex to the erosion base of the Chalupecký stream. Currently, work is being done on the restoration of the newly discovered Barbora drainage gallery. The subject of exploration work is the SDD III complex and the ODD complex - chamber K3 of the Jeroným mine NKP due to the assumptions and requirements for the mutual connection of both complexes.
3. Mining - technical and archaeological survey ODD-K3
For the purpose of the ODD survey, an in situ survey of the K3 chamber was carried out. After the inspection of the “A”-shaped chamber, its mapping and surveying were carried out using 3D technology, see Appendix P2. The following facts were found during subsequent processing and evaluation:
➤ The chamber is excavated in an ore-bearing position at a slope of 30-35° from the surface to the drainage adit, where the lower part of the chamber is flooded and the upper part is buried at the outlet. The length of the chamber in the direction of the deposit exceeds 40 m.
➤ Its atypical A-shape contains two fractures protruding against each other (positionally and height verified in the 3D model), at the place of the assumed mutual connection.
➤ Both fractures are terminated at the face by a collapse (see P2), which has flowed into the excavated passages. The horizontal distance between the two collapses is 2.8 m.
➤ The results of the survey indicate the presence of an unknown mine working. Therefore, the right break was subsequently included in the survey using laser technology and survey probes in front of the mouth to verify the solid bedrock.
➤ The right break has a total length of approximately 7.0 m with two bends. The cut is in a shallow profile. On the face there is a sandy-stony collapse with seeping water.
➤ In front of the mouth of the break in the chamber, a number of original wooden elements were found in the sediment. These are the torsos of planks, logs, beams and sidewalls of ladders, see appendix P3. Probably from the adjacent mine working. The wooden elements were stored in situ in chamber K3-ODD.
➤ In addition to the wood, an iron claw - a hook 24 cm long and 5.5 cm high at the bend, see P3. It was brought to the surface and handed over to the museum representative.
➤ In the bedrock before the break, in chamber K3, a wooden drainage trough 2.5 m long and 20 cm wide was uncovered, see Appendix P3. The trough was subsequently removed from the bedrock and placed in situ in chamber K3 opposite the mouth of the break, see Appendix P3.
➤ Apart from an iron claw 24 cm long, the metal detector survey did not yield any new finds of a metallic nature in the right part of chamber K3. In the dump of chamber K3 opposite the mouth, the remains of an iron bar oxidized on a flat stone were found. The iron objects (claw, iron torso) were handed over to the mine manager.
4. Mining - technical and archaeological survey in SDD III
After the inspection of the SDD III complex, the lower parts above the water level and the rear exit leading to the surface, ending in a collapse from the surface, were mapped. Due to the large extent of the complex, the front and middle descent were not mapped, see Appendix P4. From the exploration probe located in the middle part of the rear exit, ceramic shards were collected from the alluvial sediments and deposited at the exit point on a rocky outcrop. The exploration probe located in the middle descent of the complex at the junction was shallow to 1.0 m and did not provide any archaeological finds. In the front descent at the junction point, near the dry-laid stone foundation, the remains of a fireplace from the "fire setting" method were found. In the rock niche, there is very well-preserved charred original wood from the method used to separate the mineralized rock massif, see photo no. 1.
Photo no. 1 - View of the fireplace in a niche of the rock massif in SDD III - jumper
In the lower part of the front descent at the point of the expected connection of the complex to the secured shaft KŠ1, the remains of the original timber are found in the collapse material that flowed into the chamber, see this No. 2.
Photo no. 2 – View of the collapse that leaked into the SDD III chamber with the remains of the wood
In the upper chamber of the rear exit, under the collapses from the surface at the outcrop of the deposit, there is a profile of a blind shaft. It has a rectangular profile of 2.7 x 1.1 m, hand-carved by the ancestors in healthy granite. It is recommended to continue the exploration work that has already begun, especially in the front descent (new corridor uncovered), in the middle descent and in the lower flooded parts of SDD III in the dry season, when the water level is low. A survey was carried out in the SDD III complex with a metal detector. A number of iron objects were found, from nails from a tree trunk to fragments of irons and unidentifiable small objects of 1.0-5.0 cm in size, significantly affected by corrosion - oxidation of Fe. Of the significant finds, two complete irons of 10.5 cm and 7.5 cm in size and one torso of an iron without a tip of 7.0 cm in length were recovered. Documenting the method of disassembling a rock massif in the 16th century by ancestors using a hammer and an iron as a disassembling tool. Documentation of the finds is given in Appendix P5, which consists of a map of part SDDIII with photo documentation of the irons and the marked location of the find.
One iron with an oxidation layer 10.5 cm long was found in the upper chamber of the rear exit of the complex. The second (torso of the iron) in the sediment near the collapse of the assumed connection of the KŠ1 shaft. The third in front of the mouth of the exploration corridor above the flooded chambers of the SDD III complex. The irons were freed from sediment and a thick layer of corrosion. It is necessary to carry out further surface and deep cleaning of Fe oxides and their professional conservation. All recovered iron objects were handed over to the mine manager and museum representatives.
In accordance with the contract for the work, exploration work was carried out at the Jeroným mine in Čistá, focused on mapping the basic mining and technical conditions and collecting the discovered archaeological finds in the SDD IIl complex and the ODD complex of chamber K3. During the exploration work, the assumed position of the connection of the SDD III complex to the secured shaft KŠ1 was found. Furthermore, a blind shaft was found in the rear exit, probably connected to the following unknown mine workings. Two horizontal corridors, one of which ends after a few meters with a face and the other is significantly longer and assumes the connection of unknown mine workings. Requires further exploration. In chamber K3, two divisions were verified according to the mapping, driven towards each other and both ended with a collapse - a cone of the following mine workings. The other divisions in the chamber are ended with a face. Wooden finds from chamber K3 were stored in situ. These are wooden troughs, timber and planks, ladder sides, etc. A survey was carried out in the SDD III complex for original iron objects.
Archaeological finds in the form of irons, nails and unknown objects heavily affected by Fe oxidation were collected and handed over to the mine administrator. Significant finds in the form of three irons, documenting historical mining in the 16th century using the flail and iron disconnection tools, were documented and handed over to the museum. The finds were made near the collapse of the presumed KŠ1 shaft, in front of the mouth of the exploration corridor and in the upper chamber under the collapses at the exit of the chamber. A prospective connection of the complexes is assumed below the level of the drainage adit, i.e. below the water level of the flooded underground spaces of the Jeroným mine, where groundwater communicates with each other. A dip in the groundwater level in the flooded spaces of approximately -5 m was observed. In connection with the Barbora drainage adit and the registered groundwater table during the survey in the flooded chambers SDD II, SDD III and ODD (snapped UHPV up to -5.0 m in October 2023), a related survey and clarification of the hydrogeological and mining conditions of the lower parts of the Jeroným mine is recommended.
Appendix 1: Overview of the Jeroným mine
Appendix 2: ODD-K3 survey documentation
Appendix 3: Archaeological survey ODD-K3
Appendix 4: P4 SDD III Survey Documentation
Appendix 5: Archaeological Survey SDD III
Photo 1-3: Jeroným Mine