Penetration twin of Pyrite ("Iron Cross" twin)Your model is disabled. For more details go to Edit properties3D Model
A twin is the term applied to a rational, symmetrical intergrowth of two individual crystals of the same mineral species — rational because the two portions of the twin have a point, line, or plane in common, and symmetrical because they are related by some crystallographic symmetry operation such as reflection, translation, or rotation.
Twins may arise in several different ways, and may be classified according to their origin as growth, transformation, or gliding twins.
Twins may be descriptively classified into contact, penetration, and repeated twins.
contact twins are united to each other by the composition plane.
penetration twins are those in which two or more crystals seem to cross through each other.
repeated twins may have the individuals in parallel orientation (lamellar or polysynthetic twins) or in nonparallel orientation (cyclic twins). Cyclic twinning tends to produce circular forms.
Concept & 3D-modelling by dr. Andrei Ionut APOPEI