The X-ray diffraction method and the phosphoric acid method are widely used to determine the fraction of free silica (mainly quartz and other silica polymorphs) in respirable dust sampled in working environments in Japan. In this study, we clarified the size effect of quartz dust for the X-ray diffraction method and the phosphoric acid method using size controlled quartz samples. The quartz sam...

molybdenite occurs in five forms in the sar cheshmeh porphyry copper deposit, namely, (1)-veinlets with quartz-molybdenite, (2)-veinlets with quartz-molydenite that were filled with pyrite, (3)-veinlets with quartz-molybdenite-pyrite–chalcopyrite, (4)-molybdenite veinlets with very low quartz and (5)-disseminated molybdenite grains. because of their large size, the veinlet-related molybdenite g...

OBJECTIVES Little information is available on the quantitative risks of respiratory disease from quartz in airborne dust in the heavy clay industry. Available evidence suggested that these risks might be low, possibly because of the presence in the dust of other minerals, such as illite and kaolinite, which may reduce the harmful effects of quartz. The aims of the present cross sectional study ...

Introduction: Research into the origin of color of common varieties of quartz has shown that many longheld beliefs regarding the origin of the colored varieties are incorrect. In particular, the widely stated role of rutile inclusions in the coloration of rose and blue quartz must now be re-evaluated on the basis of new studies. Rose Quartz: Spectroscopic studies have shown that the color of ro...

A new model accounts for crystal growth patterns and internal textures in quartz cement in sandstone fractures, including massive sealing deposits, thin rinds or veneers that line open fracture surfaces, and bridge structures that span otherwise open fractures. High-resolution cathodoluminescence imaging of bridge structures and massive sealing deposits indicates that they form in association w...

A detailed oxygen isotope study of detrital quartz and authigenic quartz overgrowths from shallowly buried (<1 km) quartz arenites of the St. Peter Sandstone (in SW Wisconsin) constrains temperature and fluid sources during diagenesis. Quartz overgrowths are syntaxial (optically continuous) and show complex luminescent zonation by cathodoluminescence. Detrital quartz grains were separated from ...

Autonomous navigation systems are important to Military Operations on Urbanized Terrain (MOUT) simulations for generating realistic tactical behaviours for the non-player characters (or bots). In this paper, we describe our work on Quartz, an autonomous navigation system for MOUT simulations. Novel features of Quartz include qualitative spatial representation and hierarchical spatial reasoning ...