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Category Silicate mineral
(repeating unit)
Strunz classification 01.DB.10
Dana classification
Crystal symmetry Orthorhombic – pyramidal, H-M symbol (mm2), space group Cmc21
Unit cell a = 8.84 Å, b = 5.47 Å, c = 4.83 Å, Z = 4
Color From colorless to light gray
Cleavage None
Luster Vitreous
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.83
Optical properties Biaxial (-)
Refractive index nα = 1.740
nβ = 1.855
nγ = 1.855
Birefringence δ = 0.115
References [1][2][3]

Sinoite is rare mineral with the chemical formula Si2N2O. It was first found in 1905 in chondrite meteorites and identified as a distinct mineral in 1965. Sinoite crystallizes upon meteorite impact as grains smaller than 0.2 mm surrounded by Fe-Ni alloys and the mineral enstatite. It is named after its SiNO composition and can be prepared in the laboratory as a silicon oxynitride ceramic.[4]

Crystal structure of sinoite. Atoms: red – O, blue – N, gray – Si.[5]

The crystalline structure of silicon oxynitride is built by SiN3O tetrahedra connected through oxygen atoms along the c axis and through nitrogen atoms perpendicular to it. The strong covalent bonding of this structure results in high flexural strength and resistance to heating and oxidation up to temperatures of about 1600 °C.[6]


  1. ^ Sinoite. Handbook of Mineralogy
  2. ^ Sinoite.
  3. ^ Sinoite. Webmineral
  4. ^ A. E. Rubin (1997). "Sinoite (Si2N2O): Crystallization from EL chondrite impact melts" (PDF). American Mineralogist 82: 1001. 
  5. ^ Ohashi, Masayoshi et al. (1993). "Solid Solubility of Aluminum in O'-SiAlON". J. Am. Ceram. Soc. 76 (8): 2112–2114. doi:10.1111/j.1151-2916.1993.tb08343.x. 
  6. ^ Ralf Riedel (18 April 2008). Ceramics science and technology: Structures. Wiley-VCH. pp. 97–. ISBN 978-3-527-31155-2. Retrieved 8 October 2011.