The Ciboušov NNM covers an area of 4.96ha and was declared in 1983. The monument lies close to the town of Klášterec nad Ohří in the west of the Ústecký kraj – Ústí nad Labem Region and at the foot of the Krušné hory Mountains. The subject of the protection is a mineralogical locality where amethysts and jasper can be found around a collapsed medieval mineshaft.
The basement of the national nature monument is built of rocks of the Krušné hory crystaline complex, which are represented by fine-grained to medium-grained muscovite and two-mica orthogneiss. These rocks are estimated to be of Upper Proterozoic to Lower Paleozoic age. The quartz seams with precious quartz varieties, especially jasper and amethyst were formed in the gneisses from hydrothermal solutions in faults and crevices during repeated tectonic processes.
These thick quartz seams with precious stones such as amethysts and jasper were discovered in the 14th century. Intensive mining of precious stones took place here in the 14th and 16th centuries and in the early 19th century. Remnants of this mining, such as spoil heaps and quarry pits can still be seen at Ciboušov today.
The minerals which were extracted here were used to decorate Karlštejn castle, St. Wenceslas Chapel at Prague Castle and Tangermünde Castle near Magdeburg in Germany. This locality was rediscovered in the 1980s and extensive archaeological research, which took several years, confirmed that the same precious stone varieties which are found here were used to decorate these Medieval castles and churches.
The national nature monument lies on the slopes of the Krušné hory Mountains and is covered with non-native, mixed forest stands with predominant trees – Norway spruce (Picea abies), Scots pine (Pinus sylvestris), European larch (Larix decidua) and silver birch (Betula pendula). The flora is not exceptional and no specially protected species can be found here. The fauna also contains mostly common forest species, although the protected adder (Vipera berus) and red-backed shrike (Lanius collurio) can be found here.
This is one of the most important specially protected areas in north-western Bohemia from a mineralogical viewpoint. Ciboušov NNM and the nearby Doupňák NNM are mineralogical and archaeological sites of European importance, for the rich occurrence of precious quartz varieties.Unfortunately the whole protected area still suffers from the damage and devastation caused to this extremely valuable locality by mineral collectors.