Increasing water concentration results in the formation of hydrated silica gels and colloidal silica dispersions. Most glasses contain a metal oxide fused with silica. They are composed of silica and alumina. Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. Fly ash is composed mainly of silica and calcium oxide. Partition HPLC has been used historically on unbonded silica or alumina supports. Mineral resources include phosphorus, salt, magnesium, titanium, coal, quartz sand, clay, silica, copper. Faujasite silica is another form of crystalline silica. "" occurs when metallic oxides interact with impurities in silica sands. Diatoms build intricate hard but porous cell walls called frustules composed primarily of silica. Another common catalyst is the Phillips catalyst, prepared by depositing chromium(VI) oxide on silica. Inhalation of "crystalline" silica is harmful to the lungs, causing silicosis. Significant deposits of clay, limestone, marble, silica, and phosphate exist. Fused quartz is a glass made from chemically-pure silica. A gold film and a layer of silica aerogel provides insulation.