Orbicular Granite
Encyclopedia
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
in composition. These rocks have a unique appearance due to orbicules - concentrically
Concentric
Concentric objects share the same center, axis or origin with one inside the other. Circles, tubes, cylindrical shafts, disks, and spheres may be concentric to one another...
layered, spheroidal structures, probably formed through nucleation around a grain in a cooling magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
. Almost one third of known orbicular rock occurrences are from Finland. The occurrences are usually very small.
Places with orbicular granites
- CalderaCaldera, ChileCaldera is a port city in the Copiapó Province of the Atacama Region in northern Chile. It has an excellent harbor, protected by breakwaters, being the port city for the productive mining district centering on Copiapó to which it is connected by the first railroad constructed in Chile.-Geography...
, ChileChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far... - KuruKuru, FinlandKuru is a former municipality of Finland, now part of the town of Ylöjärvi.Kuru is located in the province of Western Finland and is part of the Pirkanmaa region. Kuru lies north of Tampere. The municipality had a population of 2,782 and covered an area of 820.48 km² of which 103.53 km² is water....
, FinlandFinlandFinland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside... - Mount Magnet, Western AustraliaWestern AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
- SavitaipaleSavitaipaleSavitaipale is a municipality of Finland.It is located in the province of Southern Finland and is part of the South Karelia region. The municipality has a population of and covers an area of of which is water. The population density is ....
, FinlandFinlandFinland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside... - Karamea, New Zealand
- Cape GeologyCape GeologyCape Geology is a low, gravel-covered point marking the west limit of Botany Bay, in the south part of Granite Harbour, Victoria Land. Charted and named by the Western Geological Party of the British Antarctic Expedition, 1910–13, who established their base here....
in Granite Harbour, McMurdo SoundMcMurdo SoundThe ice-clogged waters of Antarctica's McMurdo Sound extend about 55 km long and wide. The sound opens into the Ross Sea to the north. The Royal Society Range rises from sea level to 13,205 feet on the western shoreline. The nearby McMurdo Ice Shelf scribes McMurdo Sound's southern boundary...
, Antarctica - Taylor ValleyTaylor ValleyTaylor Valley is the southern one of the three large Dry Valleys in the Transantarctic Mountains, Victoria Land, located west of McMurdo Sound at approximately . The valley extends from Taylor Glacier in the west to McMurdo Sound at Explorers Cove at the northwest head of New Harbour in the east...
in Antarctica - Skurun, JämtlandJämtlandJämtland or Jamtland is a historical province or landskap in the center of Sweden in northern Europe. It borders to Härjedalen and Medelpad in the south, Ångermanland in the east, Lapland in the north and Trøndelag and Norway in the west...
, SwedenSwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund.... - Concordia, South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...