Hoslovice - historická těžba syenitového porfyru
General Characteristics
County (administration):
Jihočeský kraj
District (town):
Strakonice
Village:
Hoslovice
Cadastre:
Hoslovice
Map sheets:
22-34 Vimperk, 22-341 Vacov
Accessibility:
passable footpath
ID:
4237
Geology
Short characteristics of the site:
The location of the syenite porphyry is situated in a forest on the northern slope of the Chrasnice hill (elevation 711 m), 1.5 km south-east. from the village Hoslovice. About 200 m from the site passes a yellow marked hiking trail, which leads from the south from the village Hořejšice to the north to Hoslovice. The wider surroundings are being built by stromatitic biotite migmatite, and in addition to the porphyry dykes, small intrusions of biotite granite are approaching. The massive and bizarre rock log house is up to 5 m high, partly broken up into blocks of 1–5 m in size and forms a small rock town on. Porphyry was used, for example, on millstones, which have been preserved in a nearby Hoslov mill, which has been used as a museum. Flat exfoliation is noticeable, according to which the porphyry breaks into thinner decimeter plates. About 100 m lower along the slope, to the north there is another vein of syenite porphyry, the outcrop with a nicely developed subhorizontal exfoliation (d. B. SZ820) lies 130 m to the NE, but there are no traces of stone breaking. The porphyry is an atypically powerful body with a thickness of 30, maybe even 50 m, which is part of a vein only 300-400 m long, which, like all porphyry veins in the area, has a characteristic V-Z direction. Common porphyry veins tend to be 2–20 m thick, up to several kilometers long, and disintegrate more into isometric blocks, with disintegration into plates being an exception. Porphyry is a very tough rock with striking white growths of potassium feldspar 0.5-1.5 cm large. Black-brown, fine to medium-grained mafic xenoliths of phlogopite-rich rocks close to the mines of 1–30 cm are abundant. Some of them weather out negatively. Up to several mm large reddish grains in xenoliths resemble garnet, but these are reddish pseudomorphoses filled mainly with talc and actinolite.
Regional geologic unit:
Bohemian Massif > Moldanubicum > Metamorphic units in Moldanubicum > Moldanubicum of Šumava and South Bohemia
Stratigraphy:
Proterozoic - Paleozoic
Subject:
building and decorative stone, geomorphology, petrology, history
Geological phenomenon:
characteristic rock, mushroom rock, frost cliff
Genesis:
magmatic, frost weathering
Rock:
porphyry
Territorial protection
Level of protection:
Registered interesting geological localities
Conflicts of interests:
without conflicts
References
- Žáček, V. – Škoda, R. – Sulovský, P. (2009): U–Th-rich zircon, thorite and allanite-(Ce) as a main carriers of radioactivity in the highly radioactive ultrapotassic melasyenite porphyry from the Šumava Mts., Moldanubian Zone, Czech Republic. – Journal of Geosciences 54, 4, 343-354
- Žáček, V. et al. (2021): Vysvětlivky k základní geologické mapě České republiky 22-341, list Vacov. - Archiv České geologické služby, Praha
Elaboration and Updating
Elaborated by:
Vladimír Žáček, 23.01.2021
Updated by:
Citation
The database Important geological localities of the Czech Republic: 4237 [online]. Prague: Czech Geological Survey, 1998 [cit. 2023-06-16]. Available from: https:// lokality.geology.cz/4237.
Location in map:
Assessment
Scientifical assesment:
medium
Educational assesment:
middle
Significance:
regional
Representativeness:
major
Geological importance:
geo-regional value (mapping), geoturistic value
Excursion locality:
yes
Locality conditions:
no problems
You can send information about a change in the status of the site to lokality@geology.cz
