Vlčí hora, Černošín, Tachov District, Plzeň Region, Czech Republici

Regional Level Types
Vlčí hora	Hill
Černošín	Municipality
Tachov District	District
Plzeň Region	Region
Czech Republic	Country

Vlčí hora (Wolf Hill, elevation 704 m above sea level) is constituted from two similar volcanic effusions of Tertiary olivinic nephelinites with irregular bodies of pyroclastic rocks. The volcanic body (1.5 × 2.5 km) intersects chloritic-sericitic phyllites of the west Bohemian Proterozoic series. Altered pyroclastic rocks contain well-shaped phenocrysts of clinopyroxene and amphibole. Accessory olivine crystals up to 4 cm large have 84 % of forsterite component.

Kaersutitic amphibole has been found both in basanitic rocks (prevalently xenocrysts) and their tuffs (free perfect crystals) often together with clinopyroxene (“augite” de facto diopside) crystals. Phenocrysts of kaersutitic amphibole also occur in trachyandesitic rocks.

The quantity, size and near perfect form of the kaersutitic amphibole and clinopyroxene crystals has made this locality known by collectors and scientists alike. Perfectly developed, slightly molten and pitted kaersutitic amphiboles in sizes up to 15 cm has been found, normally rimmed by clinopyroxene and titanian magnetite. Kaersutitic amphibole is usually found as single crystals, however, random intergrowths of several crystals may be found.

Data from Ulrych et al. (2018) show that the compositions of kaersutitic amphiboles range from ca 0.3 apfu to 0.7 apfu Ti. The larger crystals rarely contain enough Ti to qualify as kaersutite. The majority of large crystals are more likely to be pargasite or hastingsite root name amphiboles. As the crystals must be analyzed individually to set a correct ID, the term kaersutitic amphibole is often used for these amphiboles.

The kaersutitic amphiboles from Vlčí Hora are amongst the most oxidized amphiboles known, with Fe³⁺/Fe²⁺ ratios between 7-37. They are also rich in titanium, containing between 4.28-4.63 wt% thus being intermediate between ferroan oxo-pargasite, oxo-hastingsite and kaersutite.

Located near Stříbro.

Other Regions, Features and Areas containing this locality

References