#chert  variety of silica containing microcrystalline quartz
  supertype:  #silica__silicon_oxide__siliconoxide__silicon_dioxide__silicondioxide  a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechartelierite
  subtype:  #taconite  a variety of chert containing magnetite and hematite; mined as a low-grade iron ore

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