Tetragonal system belongs to intermediate crystal family.featuresSymmetrical elementIt is a quadruple axis.Only withHigher axisThere are quadruple axes or quadruple axes in the principal axis direction of axis c ofCounter shaftCharacteristic symmetric elementcrystalIt belongs to tetragonal system.
QuadrupleHigher axisCharacteristics ofSymmetryIt determines two tetragonal crystalsCountershaftBase vectorAnd must be perpendicular to the main axis, equal in size and perpendicular to each other, that isUnit cellIt must have the shape of a square column,Cell parameterThere is a relationship between a=b ≠ c, α=β=γ=90 °.for examplerutile（TiO2）AndNickel sulfateCrystal, etc.
cassiteriteLong columnar crystals (with small crystals at the top).Please pay attentionCylinderThe edges and corners ofCrystal planeThis kind of crystal is also called "complex tetragonal" - four maincylinder, four small cylindrical surfaces.
