Orbiculite

Globular granite deposits in Chile

Ball granite from Kuru in the rock garden of the Heureka Science Center

The orbiculite (sometimes called 'orbicularite') is a magma rock with a concentrically arranged structure. In terms of appearance, the round / ellipsoidal layers can be visually distinguished from one another by composition, color and crystal size. The size of the balls is typically between 5 and 10 cm. Such structures can be found in the rock types granite ('spherical granite '), gabbro and diorite (' spherical diorite'). The spherical aggregates probably arise from crystallization in the melt around a crystallization nucleus triggered by rapid pressure loss .

There are around 90 known spheroidal granite occurrences in Finland, which is roughly half the world’s known occurrences. The reason for this is the combination of granite dominance with extensive geological research in Finland. Orbicularites are great for buildings and sculptures because of their appearance. Due to their rarity, the occurrences in Finland are under nature protection.

The orbicularite is the symbol of the Finnish province of Pirkanmaa .

Further occurrences

Despite the rare occurrence of orbicularite, more and more smaller deposits are being discovered worldwide.

in the Swedish Småland , Slättemossa as quartz monzodiorite
in Chile , Cordón de Lila as granodiorite
in Chile , Santuario de la Naturaleza Granito Orbicular as spherical granite

Individual evidence

↑ Lahti, Seppo I, Paula Raivio, and Ilkka Laitakari. Orbicular Rocks in Finland. Espoo: Geological Survey of Finland, 2005. http://arkisto.gtk.fi/ej/ej47/ej_047.pdf
↑ Orbiculit of Slättemossa in Sweden. Retrieved October 16, 2019 .
↑ Anders Lindh, Helena Näsström: Crystallization of orbicular rocks exemplified by the Slättemossa occurrence, southeastern Sweden . In: Geological Magazine . tape 143 , no. 5 , 2006, ISSN 1469-5081 , p. 713-722 , doi : 10.1017 / S001675680600210X ( cambridge.org [accessed October 16, 2019]).
↑ Hans Niemeyer Rubilar: La granodiorita orbicular del Cordón de Lila, región de Antofagasta, Chile . In: Andean Geology . tape 45 , no. 1 , November 14, 2017, ISSN 0718-7106 , p. 104 , doi : 10.5027 / andgeoV45n1-3114 ( andeangeology.cl [accessed October 16, 2019]).
↑ - TonalitL. Aguirre, F. Hervé and M. Del Campo: An orbicular tonalite from Caldera, Chile . In: Journal of the Faculty of Science, Hokkaido University, Japan . Vol. 17 (2), 1976, pp. 231-259 .

[Lahti-1] Lahti, Seppo I, Paula Raivio, and Ilkka Laitakari. Orbicular Rocks in Finland. Espoo: Geological Survey of Finland, 2005. http://arkisto.gtk.fi/ej/ej47/ej_047.pdf

[2] Orbiculit of Slättemossa in Sweden. Retrieved October 16, 2019 .

[3] Anders Lindh, Helena Näsström: Crystallization of orbicular rocks exemplified by the Slättemossa occurrence, southeastern Sweden . In: Geological Magazine . tape 143 , no. 5 , 2006, ISSN 1469-5081 , p. 713-722 , doi : 10.1017 / S001675680600210X ( cambridge.org [accessed October 16, 2019]).

[4] Hans Niemeyer Rubilar: La granodiorita orbicular del Cordón de Lila, región de Antofagasta, Chile . In: Andean Geology . tape 45 , no. 1 , November 14, 2017, ISSN 0718-7106 , p. 104 , doi : 10.5027 / andgeoV45n1-3114 ( andeangeology.cl [accessed October 16, 2019]).

[5] - TonalitL. Aguirre, F. Hervé and M. Del Campo: An orbicular tonalite from Caldera, Chile . In: Journal of the Faculty of Science, Hokkaido University, Japan . Vol. 17 (2), 1976, pp. 231-259 .