Polarized light micrograph of a thin section of marble. Marble, a metamorphosed granular limestone protolith, is a calcite that has been recrystallized by intense pressure and heat in metamorphism. It has a granoblastic texture consisting of an arrangement of anhedral (without well-developed crystal faces) phaneritic (macroscopic) equi-granular mineral in a metamorphic rock. In the image, each grain of calcite crystal shows sutured edges and lamellar twinning crystals that look like stripes arranged in a pattern, parallel to the diagonals of his rombohedral cleavage. Its chemical composition is CaCO3 (calcium carbonate). Marble takes a high polish and it is used worldwide in sculpture and architecture. Field of view size: 0.74 x 1.12 mm (0.029 x 0.044 in)