Empirical Formula: O₂Si 
Molecular Weight: 60.0843
IUPAC Name: dioxosilane
Stability: Stable from 870–914° at atmospheric pressure, but persists as a metastable phase below 8°C forming low tridymite below 1°C and middle tridymite from 117–1°C. IDLH 25 mg/m³
Appearance: White or colorless platelets or orthorhombic crystals 
Synonyms: Silica ; Quartz ; Cristobalite ; Sand ; Dioxosilane ; Diatomite ; Tridymite ; Aerosil ; Silicic anhydride
Following is the molecular structure of Silica , Cristobalite&ndash ; Tridymite (15468-32-3):

Consensus  of Silica , Cristobalite&ndash ; Tridymite (15468-32-3):
NTP 10th Report on Carcinogens. IARC Cancer Review: Group 2A IMEMDT    IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man . 7 ,1987,p. 341.(World Health Organization, Internation Agency for Research on Cancer,Lyon, France.: ) (Single copies can be ordered from WHO Publications Centre U.S.A., 49 Sheridan Avenue, Albany, NY 12210) ; Animal Sufficient Evidence IMEMDT    IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man . 42 ,1988,p. 209.(World Health Organization, Internation Agency for Research on Cancer,Lyon, France.: ) (Single copies can be ordered from WHO Publications Centre U.S.A., 49 Sheridan Avenue, Albany, NY 12210) ; Human Limited Evidence IMEMDT    IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man . 42 ,1988,p. 209.(World Health Organization, Internation Agency for Research on Cancer,Lyon, France.: ) (Single copies can be ordered from WHO Publications Centre U.S.A., 49 Sheridan Avenue, Albany, NY 12210) .

Confirmed carcinogen with experimental tumorigenic data. Poison by intratracheal route. Human systemic effects by inhalation: cough, dyspnea. About twice as toxic as silica in causing silicosis. Mutation data reported.      

 Standards of Silica , Cristobalite&ndash ; Tridymite (15468-32-3):
OSHA PEL: Total Dust: TWA 30 mg/m³/2(%SiO₂+2) TWA 0.05 mg/m³
ACGIH TLV: (Silica, Crystalline) TWA Respirable Fraction: 0.05 mg/m³
DFG MAK: 0.15 mg/m³
NIOSH REL: TWA 50 µg/m³

For occupational chemical analysis use OSHA: #ID-125G or NIOSH: Silica, crystalline (XRD), 7500; (Color), 7601; (IR), 7602.