GENERAL GEOLOGY

Detailed explanation-1: -The unique symmetry operation in an orthorhombic system is The unique symmetry operation in an orthorhombic system is 2/m 2/m 2/m – Three twofold axis of rotation coinciding with the three crystallographic axes.

Detailed explanation-2: -The orthorhombic unit cell is distinguished by three lines called axes of twofold symmetry about which the cell can be rotated by 180° without changing its appearance. This characteristic requires that the angles between any two edges of the unit cell be right angles but the edges may be any length.

Detailed explanation-3: -An orthorhombic dipyramid is a closed-form (It can totally enclose space). The symmetry of the dipyramidal Class (3 mutually perpendicular 2-fold axes of rotation, each perpendicular to a mirror plane, and a centre of symmetry) requires the dipyramid.

Detailed explanation-4: -There are six (6) elements of symmetry in crystals: a Center of Symmetry, an Axis of Symmetry, a Plane of Symmetry, an Axis of Rotatory Inversion, a Screw-axis of Symmetry, and a Glide-plane of Symmetry.

Detailed explanation-5: -Thus, there are 3 axial planes of symmetry present in the normal class of orthorhombic system (i.e. in olivine as discussed above).