Porcellanite is a term conventionally used for multicoloured jasper-like rocks, formed from clays by pyrometamorphism. In the territory of the Most Basin, however, all pyrometamorphic rocks produced by natural fossil combustion of a Neogene coal seam are traditionally marked by the term…

The rich occurrence of well-crystalline rare Al-hydroxide, nordstrandite, was found in the Děpoltovice quarry near Karlovy Vary, western Bohemia (Czech Republic). It forms there several morphological types and in the studied association, gibbsite was not found. This is atypical in comparison with…

The Roztoky Intrusive Centre (RIC) represents a complicated multiple intrusive structure combining large elliptical crater vent (3 km by 1.5 km) filled by products of superficial trachytic and minor basaltic volcanism with trachytic and phonolitic intrusions, accompanied by hypabyssal intrusions of…

Currently, we regard pegmatites as rocks displaying more or less different mineral composition, provided that these display pegmatite-like textures (grain size, zonation, skeleton crystals development, graphic intergrowths, etc.). Like common granitic pegmatites, they also originated by…

In the area of the dumps of the Staročeské pásmo zone (mine dump Stará Plimle) at Kaňk near Kutná Hora (Czech Republic) a new occurence of arsenic supergene mineralization has been found. The association of supergene minerals is similar to original findings from the Kuntery and Šafary medieval…

Granitic pegmatite vein (ca. 15 cm thick) containing Be-minerals occurs in granite from the Sitina tunnel in Bratislava, SW Slovakia. Dark grey quartz, white to dark grey microcline, milky-white albite (partially variety cleavelandite) and muscovite are main minerals of the pegmatite. Accessory…

A serpentinite quarry at Bernartice near Dolní Kralovice is further locality where relatively rare Mg-carbonate huntite was identified. The mineral was found in a vein striking 35 - 45o and dipping 70o to the west that is 10 - 25 cm thick and penetrates the altered serpentinite. The vein is filled…

The article presents new knowledge on a study of silica rock (limnosilicite) with electron microscopy on the locality Banské in the Slanské vrchy Mts., Eastern Slovakia. We studied five colour varieties of silicites - black, light brown, dark brown, gray and white color, and the cause of these…

The peraluminous granite dykes and small bodies on the south-western margin of the Třebíč pluton consist of variable proportions of quartz, K-feldspar, sodic plagioclase (An1-7), disseminated tourmaline (XFe = 0.60 - 0.92, Al = 6.57 - 7.10 apfu, Na 0.32 - 0.63 apfu), muscovite and common annite.…

Interesting calcite veins with fluorite have been found in bituminous limestones in abandoned quarry near the Lipovník village. Fluorite forms dark purple to nearly black aggregates up to 1.5 cm which are composed of euhedral usually deformed cubic crystals up to 7 mm in size. Other associated…

Metastable carbonate phase ikaite (CaCO3.6H2O) was determined by an X-ray powder diffraction to be a dominant mineral phase formed on a surface of seasonal cave ice formations in the Koda Cave in Bohemian Karst (Czech Republic). In one of the samples also the possible presence of a mineral…