The properties and uses of silica (7631869) and organosilicon compounds are reviewed. Silica is the second most common element on earth, occurring as quartz (14808607), feldspar, and kaolinite (1318747). It is used for alloys as a hardener, for semiconductors, and in the production of silanes and silicones. The physical characteristics of silane (7803625), trichlorosilane (10025782), and tetrachlorosilane (10026047) are given. Siloxanes contain oxygen (7782447), hydrogen (1333740), carbon (7440440), and silicon, and are used for resins, elastomers, and oils. Resins are incorporated into paints, plastics, and foams. Elastomers are used for biological implants. Oils are used as lubricants and water repellants and are utilized for the prevention of contact eczema. Silicone oils may sometimes irritate the ocular mucosa. The physical properties of two heterosiloxanes, methyl-silicate (4421958) and ethyl-silicate (78104), are presented. Heterosiloxanes are dangerous because they contain toxic metals that are soluble in water. Methyl-silicate may cause ocular ulceration, and lung and kidney damage if the vapors are inhaled. Ethyl-silicate causes similar symptoms, but at much higher concentrations. The author concludes that eye protection must be worn for the more volatile organosilicon compounds.