(April 2015) Corruption in Brazil exists on all levels of society from the top echelons of political power (as seen in the MensalÃ£o Scandal and the Operation Car Wash and the Petrobras scandals) to the smallest municipalities.
Quartz sands, which are high in silica content, are used to make glass. When quartz sands are crushed they produce particles with sharp, angular edges that are sometimes used to make sandpaper for smoothing wood. Some quartz sand is found in the form of sandstone.
The primary formers used for making Pyrex include silica sand and boric acid. Silica sand is also known as silicon dioxide. It is a crystalline material and was probably the major component of the first glass used by humans. In a typical Pyrex glass composition, silicon dioxide makes up about 60-80% by weight.