Crystal twinning
![Diagram of twinned crystals of Albite. On the more perfect cleavage, which is parallel to the basal plane (P), is a system of fine striations, parallel to the second cleavage (M).](/Images/godic/202502/18/Twinned_crystals_of_Albite0428.png")
![Quartz - Japan twin](/Images/godic/202502/18/Quartz_Japan_Twin_Huaron_Peru0428.jpg")
![Twinned pyrite crystal group](/Images/godic/202502/18/Pyrite_606080428.jpg")
![Galvanized surface with macroscopic crystalline features. Twin boundaries are visible as striations within each crystallite, most prominently in the bottom-left and top-right.](/Images/godic/202502/18/Galvanized_spangle0428.jpg")
Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals. Crystallographers classify twinned crystals by a number of twin laws. These twin laws are specific to the crystal system. The type of twinning can be a diagnostic tool in mineral identification.