Crystals along with suitable examples are listed in the table.
|System||Axial distances||Axial angles||Examples|
|Cubic||a = b = c||α = β = γ = 90°||NaCl,KCl, Diamond, Cu, Ag|
|Tetragonal||a = b ≠ c||α = β = γ = 90°||White tin,SnO2|
|Orthorhombic||a ≠ b ≠ c||α = β = γ = 90°||Rhombic — Sulphur, KNO3, K2 SO4, BaSO4, PbCO3|
|Monoclinic||a ≠ b ≠ c||α = γ = 90°, β ≠ 90°||Monoclinic sulphur, Na2 SO4 .10H2O|
|Hexagonal||a = b ≠ c||α = β = 90°, γ = 120°||Graphite, ZnO, CdS|
|Rhombohedral||a = b = c||α = β = γ ≠ 90°||Calcite, quartz, NaNO3|
|Triclinic||a ≠ b ≠ c||α ≠ β ≠ γ ≠ 90°||CuSO4.5H4O, K2Cr2O7|
In the above description, it was assumed that the particles are present only at the corners of the unit cells. Such type of unit cells in which particles are present only in the corners are called Simple Unit Cells.
But it has been observed that the particles may also be present at some other special positions within the unit cell. Such unit cells are called non-primitive unit cells.