A form of pneumoconiosis in rural African women termed "Transkei silicosis" has been thought to be due to silica particles inhaled while they are hand grinding maize between rocks. Twenty five women were studied who were considered to have this condition according to the following criteria: rural domicile, radiographic and lung biopsy evidence of pneumoconiosis, no exposure to mining or industr...

Quartz (α-quartz), is the most common crystalline silica polymorph in nature and is the only polymorph found in significant concentrations in coal and in coal ash. Since exposure to quartz is liable to cause lung diseases, it is very important to know the concentration of biologically active quartz in respirable particles in order to evaluate their effect on the workers in contact with them. Th...

OBJECTIVES To describe the radiographic changes in coalworkers exposed to unusual concentrations of respirable quartz during the 1970s, and to relate these to exposure measurements. METHODS Men who had worked at one Scottish colliery during the 1970s were invited to a health survey. Chest radiographs were taken from 547 subjects. Classifications of these films under the International Labour O...

the borujerd complex of western iran is composed of intrusions and their surrounding contact aureole, with, pegmatites and quartz veins. pegmatites differ in mineralogy, origin and age, and two groups can be distinguished. the older pegmatites (about 120 ma age) intruded contact metamorphic rocks from the early magmatic stage, while the younger pegmatites (52-70 ma age) formed during the late m...

OBJECTIVES To quantify personal time-weighted average respirable dust and quartz exposure on a sandy, a sandy loam, and a clay soil farm in the Free State and North West provinces of South Africa and to ascertain whether soil type is a determinant of exposure to respirable quartz. METHODS Three farms, located in the Free State and North West provinces of South Africa, had their soil type conf...

Uniformly-sized, single-crystal alpha-quartz nanospheres have been synthesized at 200 °C and 15 atm under continuous stirring starting from uniform, amorphous Stöber silica colloids and using NaCl and alkali hydroxide as mineralizers. Quartz nanosphere size is controlled by the colloid particle size via direct devitrification. Uniform, high-purity nanocrystalline quartz is important for underst...

[1] The anelastic response of single-crystal and polycrystalline quartz and quartz-rich sandstones to applied stress at low frequencies has been investigated by dynamic mechanical analysis and force torsion pendulum measurements. The dynamic modulus was measured on heating and cooling through the a-b phase transition under shear and bending stress applied at low frequency (~1Hz). Single crystal...

Phagocytosis of quartz particles by rabbit alveolar macrophages and monocytes and human granulocytes and monocytes was accompanied by stimulation of substrate free reduction of nitroblue tetrazolium to formazan. This reflects activation of an oxygen dependent bactericidal system of phagocytes and total (exogenic and endogenic) generation of active oxygen species. Low fibrogenic and cytotoxic al...

in the asemi-gawa area of intermediate high-pressure and low-temperature sanbagawa metamorphic belt in central shikoku, japan, piemontite-quartz schists are common in which cation exchange between piemontite and garnet has been studied. piemontite in contact with garnet usually contains two zones in which core is enriched in mn3+ and surrounded by a rim rich in fe3+. garnet is ca-fe-bearing spe...

The quantitative mineralogical analysis of small samples (less than 20 mg) of china clay has been investigated using x ray diffractometry to determine kaolinite, mica, quartz, and feldspar. A method has been developed and applied to the quantitative analysis of airborne dust samples and of other small discrete samples. Determinations were made either on samples after collection on a membrane fi...