PumiceThe pumice rock is the lightest rock in the world and is the onlyrock in the world that can float in the water. It can float in thewater because of the special way it was cooled. The pumice rockcooled very fast therefore it is very light and that it also cooledunderwater that causes the holes in the rock. People use therocks for rubbing of dead skin from their feet. It looks a bit likecoral. It has a very rough texture and that’s why they use it torub off dead skin. Pumice is also used as insolation or as a handsoap ingredient.
GraniteGranite as said before is similar to marble and is also used forkitchen countertops and floors or statues. Granite is the mostused rock for everyday life for example most buildings havegranite in it. A lot of pebbles on the ground are granite. Likemarble it is cooled very slowly and has almost the exact samesized crystals as marbles. Granite is the most common rock onthe earths surface. Granite has a pretty rough texture. Peoplesometimes use granite for rock climbing walls.
BasaltBasalt is very smooth and hard rock that is made whenvolcanoes spit out pieces of lava. Basalt is also very common onthe earths surface like granite but is the most common rockunderground. Basalt has very small crystals so it cooled veryquickly but not as quickly as pumice which doesn’t have crystalsat all. Basalt can be found on the Moon, Mars and even Venus.Since Basalt is very hard people used to very often use basalt asa grinding stones for mills to make wheat out of grains. Basalt isvery often used for asphalt.
ObsidianObsidian is a very smooth and shiny rock that is also known asnatural glass. A lot of people used to use obsidian to makearrowheads or fishing hooks because it can be very sharp. Alot of surgeons today use obsidian knives for eye surgery orother things. The stone aged people often wanted obsidianbecause it was sharper than flint and was very practical backthen. Obsidian also cools very slowly so it has few crystalseven though it is very shiny. Obsidian is very brittle andtherefore can be chipped very easily, which is why the stoneaged wanted it. Obsidian sometimes come very rarely coloredblue, yellow, red or orange.
ScoriaScoria is a red, brown, or black and is also referred to volcanicrock. Scoria was cooled a bit slower then pumice but alsounderwater that is why it has holes in it like the pumice rock. Thename scoria comes from the Greek and means rust, probablybecause it can be red as rust as seen below in the picture. Scoriais often used in high temperature isolations, and landscaping anddrainage works. Some statues on Easter Island have scoria inthem.
Facts• Igneous rocks are the most common rocks used for buildings• Mount Rushmore is made out of igneous rocks• The word igneous comes from the Latin and means fire, because igneous rocks come from volcanos.• Did you know that basalt which is an igneous rock is one of the heaviest and densest rocks in the world.• Did you know that most of the Empire State Building is made of igneous rocks.• Thousands of years ago people carved their homes out of soft igneous rocks.