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The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
Solidified lava flow in Hawaii Sedimentary layers in Badlands National Park, South Dakota Metamorphic rock, Nunavut, Canada. Geology (from Ancient Greek γῆ (gê) 'earth' and λoγία () 'study of, discourse') [1] [2] is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. [3]
Territory Guide #1 - Newfoundland: Rock of Ages: Information, maps and adventure ideas for locations in Newfoundland: 2004 Trail Guide: The Great Northwest: Information, maps, several Savage Tales and a mini Plot Point campaign set in Montana, Oregon, Washington, and Idaho. 2010 Trail Guide: South o' the Border
Though most understanding of rocks comes from those of Earth, rocks make up many of the universe's celestial bodies. In the Solar System, Mars, Venus, and Mercury are composed of rock, as are many natural satellites, asteroids, and meteoroids. Meteorites that fall to Earth provide evidence of extraterrestrial rocks and their composition. They ...
An Adventurer's Guide to Eberron is an accessory for the Eberron setting that is an illustrated 64-page visual guide to the world of Eberron. Kevin Kulp wrote that "the adventuring races are one of the first things shown. Shifters, changelings, elves, orcs, warforged, kalashtar, and all the other races are richly illustrated and spotlighted.
The third form of rock material found on Earth is metamorphic rock, which is created from the transformation of pre-existing rock types through high pressures, high temperatures, or both. The most abundant silicate minerals on the Earth's surface include quartz , the feldspars , amphibole , mica , pyroxene , and olivine . [ 25 ]
Igneous rock (igneous from Latin igneus 'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.
The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history, and mark the start of the Archean Eon, which is defined to start with the formation of the oldest intact rocks on Earth.