Explanatory notes
… agglomeration of quartz crystals with feldspar and mica. It varies in colour (grey, green, pink, red, etc.) according to … oxide. Porphyry is a finely grained, slightly translucent variety of granite. Sandstone is a rock of sedimentary … other hard igneous rocks (e.g., syenite, gneiss, trachyte, lava, diabase, diorite, phonolite), as well as calcareous …