Abstract: A method of separating heavy mineral particles, such as zircon, monazites, xenotime etc., from a sample of quartz crystal powder, comprises the steps of: a. conditioning the quartz powder suspected of containing heavy mineral particles as an aqueous pulp using a froth-flotation agent; b. subjecting the conditioned pulp to froth flotation to obtain a tailing; c. combining the tailing with an aqueous solution having a density greater than that of quartz and less than that of a heavy mineral which it is desired to separate; and d. centrifuging the combination. The separated heavy mineral crystals can then be characterized using a micro-analysis technique.

Abstract: Processes for the manufacture of a hollow cylindrical porous body of synthetic vitreous silica soot by outside vapor deposition on a mandrel are described, in which the temperature of the mandrel is controlled to be substantially constant throughout the deposition process. In preferred embodiments, the mandrel is composed of metal or metal alloy. Hollow ingots of pure or doped synthetic vitreous silica glass manufactured by such processes are also described.

Abstract: Methods are described for manufacturing silica-based glass, in which silica precursor material is supplied to a synthesis flame in the form of an emulsion. The methods involve the steps of: forming an emulsion of an aqueous phase in a non-aqueous liquid silica precursor material; supplying the emulsion as a spray of droplets into a synthesis flame, whereby the precursor material is converted in the flame into a silica-containing soot; and collecting the soot on a substrate, either as a porous soot body for subsequent consolidation to glass or directly as a substantially pore-free glass.

Abstract: Processes for the manufacture of a hollow cylindrical porous body of synthetic vitreous silica soot by outside vapour deposition on a mandrel are described, in which the temperature of the mandrel is controlled to be substantially constant throughout the deposition process. In preferred embodiments, the mandrel is composed of metal or metal alloy. Hollow ingots of pure or doped synthetic vitreous silica glass manufactured by such processes are also described.

Abstract: Hollow ingots of transparent synthetic vitreous silica glass of external diameter greater than 400 mm and internal diameter greater than 300 mm are disclosed. The ingots are substantially free from bubbles or inclusions greater than 100 ?m in diameter, have no more than 100 ppB of any individual metallic impurity, and have chlorine concentration less than 5 ppM. Also disclosed are methods for producing such ingots, in which a porous soot body of density greater than 0.4 g/cm3 is deposited on an oxidation resistant mandrel. The soot body is dehydrated on a mandrel comprising graphite, carbon fibre reinforced carbon, silicon carbide, silicon impregnated silicon carbide, silicon carbide-coated graphite or vitreous silica, either under vacuum or in the presence of a reducing gas, and then sintered to transparent pore-free glass under vacuum or in an atmosphere of helium.

Abstract: Methods are described for manufacturing silica-based glass, in which silica precursor material is supplied to a synthesis flame in the form of an emulsion. The methods involve the steps of: forming an emulsion of an aqueous phase in a non-aqueous liquid silica precursor material; supplying the emulsion as a spray of droplets into a synthesis flame, whereby the precursor material is converted in the flame into a silica-containing soot; and collecting the soot on a substrate, either as a porous soot body for subsequent consolidation to glass or directly as a substantially pore-free glass.