Calcite after calcite pseudomorph coated by limonite on quartz

One very old cabinet size specimen of quartz, covered with steep scalenohedron calcite crystals, build in the alternation of several generations of calcite and quartz very thin ( less than a millimeter) layers. Later on, these scalenohedron crystals were coated by limonite. At the end of crystallization process appear white, flat rhombohedron calcite crystals.