# 7-types of crystals:

On the basis of axial length in x,y, z-direction, and interfacial angles between them,unit cell can be classified into seven types which are called**Seven Crystal System.**

7- Crystal Habits | Axial Length | Interfacial Angles |

Cubic | a = b = c | α = β = γ = 90˚ ^{} |

Tetragonal | a = b ≠ c | α = β = γ =90˚ ^{} |

Orthorhombic(Rhombic) | a ≠ b ≠ c | α = β = γ =90˚ |

Monoclinic | a ≠ b ≠ c | α = γ =90˚ , β ≠ 90˚ |

Triclinic | a ≠ b ≠ c | α ≠ β ≠ γ ≠ 90˚ |

Hexagonal | a = b ≠ c | α = β = 90 ˚ , γ =120˚ |

Rhombohedral | a = b = c | α = β = γ ≠ 90˚ |

α,β,γ is the interfacial angle between x-axis and y-axis, y-axis and z-axis, z-axis and x-axis respectively.

### Note:

**Most symmetric crystal -Cubic Crystal**

**Most unsymmetric crystal -Triclinic Crystal**To remember this crystal system we have derived a formula and i.e.

CUTE OUR MOTHER

CU-Cubic

TE-tetragonal

OUR-Orthorhombic

MO-Monoclinic

T-Triclinic

HE-Hexagonal

R-Rhombohedral