Mono-crystalline nanometer high cristobalite glass-ceramic from nominal pyroxene glass

Transparent glass was prepared from nominal alkali pyroxene (Na2 Mg Si2O6) composition. Incorporation of Cr2O3 in alkali pyroxene composition in two % (0.5 and 1.0) increases the crystallization temperature. High cristobalite was developed alone in all glass samples heat-treated at 800°C. The microstructure shows nanometer crystals of high cristobalite which spread in glassy matrix. The densities, hardness and coefficient of thermal expansion were between 2.49 and 2.53 g/cm3, 505 and 611 kg/mm2 and between 9.38 and 13.32 x 10− 6°C− 1 (30–300 ˚C ) respectively. The antimicrobial activity of the prepared glass and ceramics shows that the only samples contain 1% of Cr2O3shows an inhibition zone in case of Candida albicans yeast.

STRUSKY PO TAVBĚ POLYMETALICKÝCH RUD Z LOKALITY ČEJKOV-TRSOV (PELHŘIMOVSKÝ RUDNÍ REVÍR)

Slags after smelting of polymetallic ores occur at the locality Čejkov-Trsov which represents medieval smelting site and lies approximately 1 030 m SE from the center of the Čejkov village. Samples collected during archaeological excavation were obtained from the Museum Vysočiny Jihlava. Bulk chemical analyses show that studied slags are dominated by SiO2-FeO-Al2O3 oxides (sum of these three components is 75.27–88.81 wt. %). Unusual are high barium (up to 9.2 wt. % of Ba) and lead contents (up to 15.0 wt. % of Pb) as well as low zinc contents (230–3780 ppm). All samples except one are generally CaO poor (an exception is sample CT4 containing 6.03 wt. % CaO) which probably refl ect lack of CaO – based additives. Light microscopy and EDS analyses on an electron microprobe proved following phases: spinelides, olivine, feldspars, pyroxene, glass and quartz. Spinelides are the most variable in their composition ranging from almost pure magnetite (92 mol. % of magnetite, 5 mol. % of spinel and 3 mol. % of galaxite) to spinel-rich hercynite (50 mol. % of hercynite, 45 mol. % of spinel and 5 mol. % of magnetite). Olivine is represented by fayalite (89–90 mol. % Fa, 5–7 mol. % Te, 4–5 mol. % Fo). Newly formed feldspars are present in all studied samples and contain up to 22.8 wt. % of BaO (44–50 mol. % of orthoclase, 40–47 mol. % of celsiane and 9–11 mol. % of albite). Ca-Fe pyroxene (Fs52Wo38En11–Fs51Wo37En13) was formed probably due to high enough temperature and a sufficient CaO content. Cracked quartz grains are present within all samples. They were more or less corroded by a slag melt.