Dacite ( / ˈ d eɪ s aɪ t /) is an igneous, volcanic rock.It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite.The word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains (now modern Romania and Moldova) where the rock was first described.
Diorite forms if this type of melt crystallizes below the surface. Diorite is usually composed of sodium-rich plagioclase with lesser amounts of hornblende and biotite. It usually contains little if any quartz. This makes diorite a coarse-grained rock with a contrasting mix of black and white mineral grains. Students often use this "salt and pepper" appearance as a clue to the identification of diorite.
Diabase is the preferred name in North America, yet dolerite is the preferred name in most of the rest of the world, where sometimes the name diabase is applied to altered dolerites and basalts. Many petrologists prefer the name microgabbro to avoid this confusion.
Limestone is a common, chemical sedimentary rock formed primarily from calcium carbonate. It is generally light-colored and can also include fossils of calcium carbonate-containing organisms, like corals. Limestone can be found all over the world and is the major type of rock found in karst features (crystal cave systems found in bedrock).
Sandstone is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material. It also contains a cementing material that binds the sand grains together and may contain a matrix of silt- or clay-size particles that occupy the spaces between the sand grains.