33:
73:
61:
262:
colour with lighter and darker shades of grey oval shaped or orbicular inclusions. Orbiculite has been used to make jewellery and other decorative items in the past, but due to its rarity in South Africa, it is not commercially exploited and has become more a curiosity due to it being considered something of an enigma in geology. The geology of the surrounding area can be described as gneissic and granitic and is better known for its once rich copper deposits. The rocks of this region form part of the mid
755:
SimĂ”es, Margarida C.; "OcorrĂȘncia de granito orbicular em Couto do Osso, Serra da Peneda", in: Margarida C. SimĂ”es, Armando
Moreira: Volume de homenagem ao Professor Doutor Carlos Teixeira / Sociedade Geológica de Portugal ; introdução Décio Thadeu & Fernando Real. - Lisboa : Sociedade
261:
and one of just two known occurrences in South Africa. Another occurrence is on the farm
Nigramoep just north west of Nababeep. This location has unfortunately been impacted by blasting for copper mining and has not been rehabilitated. When cut and polished, the granite has a very attractive pinkish
206:, clinopyroxene, and accessories, mainly magnetite. The texture is hypidiomorphic granular. There is a close petrographic similarity between the core of the orbicules, the non-orbicular inclusions and country rock. The site has been declared a protected area ("Santuario de la Naturaleza").
419:
257:, South Africa, just west of the small town of Concordia, there is a rare occurrence of orbicular granite. The outcrop, known as Orbicule Hill or "wonderkoppie" (as it is locally known), is a
467:"Lahti, S. (Editor) Orbicular Rocks in Finland 2005, with contributions by P. Raivio and I. Laitakari.: Espoo (Geological Survey of Finland) 2005. ISBN: 951-690-911-6. Price âŹ30, 177 pp"
466:
198:. The core of the orbicules is polycrystalline and corresponds to a medium gray, medium grained (1.5 to 2.0 mm) quartz diorite composed of plagioclase, amphibole,
728:
766:
Enz, Robert D.; Kudo, Albert M.; Brookins, Douglas G. (February 1979). "Igneous origin of the
Orbicular Rocks of the Sandia Mountains, New Mexico".
803:"Role of the Bundelkhand Granite Massif and the Son-Narmada megafault in precambrian crustal evolution and tectonism in Central and Western India"
258:
620:
595:
174:. The surface ratio of matrix/orbicules is 35/65; orbicules are mainly ellipsoidal with an average axis of 7.0 cm and are composed of a
32:
302:
38:
378:
500:
Aguirre, Luis L.; Hervé, Francisco A.; Campo, Mónica del (September 1976). "An orbicular tonalite from
Caldera, Chile".
60:
72:
288:
528:
240:
age. The orbs are characterized by a single shell of 1 to 10 mm composed of radial plagioclase, quartz, and
735:
161:
236:, in 2017. The orbicular body consists of an irregular dyke of 75 m and is hosted by a granodiorite of
775:
431:
321:
297:
488:
704:
420:"Crystallization of orbicular rocks exemplified by the SlÀttemossa occurrence, southeastern Sweden"
447:
348:
241:
692:
616:
591:
334:
214:
178:
core and a single dark shell with a predominantly radial texture composed of equal amounts of
164:
and the orbicular body is characterized by a zone of comb layering. The orbicular body has a
112:
119:
due to rapid physical changes. Almost one third of known orbicular rock occurrences are from
830:
783:
542:
509:
439:
387:
232:
A rare type of orbicular rock (locally known as
Chaitenita) was discovered in Cerro Recoba,
222:
221:. The orbicular granodiorite occur in the form of a pipe that is part of the more extensive
218:
171:
636:
779:
502:
Journal of the
Faculty of Science, Hokkaido University. Series 4, Geology and Mineralogy
435:
533:
372:
175:
150:
138:
77:
65:
824:
802:
657:
451:
365:
352:
312:
282:
187:
116:
96:
669:
330:
292:
278:
210:
168:
570:
394:
339:
306:
263:
254:
179:
165:
588:
Geological
Journeys: A Traveller's Guide to South Africa's Rocks and Landforms
572:
La granodiorita orbicular del Cerro Recoba, Batolito Patagónico Norte, Chaitén
443:
233:
226:
203:
153:-like with an exposed surface area of approximately 375 m, enclosed in a
108:
547:
529:"La granodiorita orbicular del CordĂłn de Lila, regiĂłn de Antofagasta, Chile"
356:
195:
183:
157:
787:
115:
structures, probably formed through nucleation around a grain in a cooling
382:
325:
154:
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52:
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surrounding different kinds of igneous and, possibly, metamorphic cores.
343:
316:
237:
191:
120:
100:
23:
513:
360:
199:
142:
71:
59:
613:
Aspects of the history of copper mining in
Namaqualand, 1846-1931
756:
GeolĂłgica de
Portugal, 1981. - p. 125-128. Cota:7-294 NBP 30944
225:
of El LeĂłn. Magmas forming these rocks cooled into rock in the
637:"British Antarctic "Terra Nova" 1910-1913 Expedition Reports"
103:
in composition. These rocks have a unique appearance due to
266:
Eon and formed approximately one billion years ago.
46:
418:Lindh, Anders; NÀsström, Helena (September 2006).
729:"Areas of Geological Interest in County Donegal"
37:Polished rock sample of orbicular granite from
8:
137:On the coastline eleven kilometres north of
16:
575:(Thesis) (in Spanish). University of Chile.
275:Powell River Area, British Columbia, Canada
807:Journal of the Geological Society of India
123:. The occurrences are usually very small.
31:
546:
705:"Orbiculit von SlÀttemossa in Schweden"
586:Norman, Nick; Whitfield, Gavin (2006).
407:
15:
160:. Where visible, the contact between
7:
413:
411:
76:Close-up of orbicular granite near
658:Te Ara Encyclopedia of New Zealand
64:Outcrop of orbicular granite near
14:
186:accompanied by lesser amounts of
527:Niemeyer Rubilar, Hans (2018).
39:Mount Magnet, Western Australia
465:Konopelko, D. (1 April 2006).
1:
489:Orbicular rocks vs. Rapakivis
674:Nelson Rock and Mineral Club
611:Smalberger, John M. (1975).
202:, biotite, small amounts of
149:orbicular granite which is
847:
801:Basu, Adhir Kumar (2007).
379:Peneda-GerĂȘs National Park
444:10.1017/S001675680600210X
51:
30:
21:
548:10.5027/andgeoV45n1-3114
259:provincial heritage site
788:10.1130/GSAB-P2-90-349
774:(2 Part II): 349â380.
736:Donegal County Council
693:Hultsfred municipality
471:Mineralogical Magazine
99:type which is usually
81:
69:
569:Soto, AnĂbal (2019).
145:, there is a body of
75:
63:
670:"Sites and Sections"
322:Matobo National Park
298:Karamea, New Zealand
281:in Granite Harbour,
780:1979GSAB...90..349E
436:2006GeoM..143..713L
424:Geological Magazine
18:
82:
70:
709:www.kristallin.de
622:978-0-86977-043-6
597:978-1-77007-062-2
390:, New Mexico, USA
335:Western Australia
95:) is an uncommon
85:Orbicular granite
58:
57:
17:Orbicular granite
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388:Sandia Mountains
303:Split Apple Rock
270:Other localities
219:Salar de Atacama
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87:(also known as
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5:
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628:
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537:(in Spanish).
534:Andean Geology
519:
508:(2): 231â259.
492:
480:
457:
430:(5): 713â722.
406:
405:
403:
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399:
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391:
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373:County Donegal
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215:CordĂłn de Lila
207:
176:quartz diorite
133:
130:
128:
125:
109:concentrically
89:orbicular rock
78:Caldera, Chile
66:Caldera, Chile
56:
55:
49:
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28:
27:
13:
10:
9:
6:
4:
3:
2:
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832:
829:
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826:
813:(5): 745â770.
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477:(2): 238â239.
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397:Massif, India
396:
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389:
386:
384:
380:
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371:Mullaghderg,
370:
368:in Antarctica
367:
366:Taylor Valley
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283:McMurdo Sound
280:
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209:An orbicular
208:
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188:clinopyroxene
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117:magma chamber
114:
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97:plutonic rock
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67:
62:
54:
50:
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34:
29:
26:
25:
20:
810:
806:
796:
771:
768:GSA Bulletin
767:
761:
751:
739:. Retrieved
723:
712:. Retrieved
708:
699:
688:
677:. Retrieved
673:
664:
653:
641:. Retrieved
631:
612:
606:
587:
581:
571:
564:
552:. Retrieved
538:
532:
522:
505:
501:
495:
483:
474:
470:
460:
427:
423:
331:Mount Magnet
293:South Africa
285:, Antarctica
279:Cape Geology
252:
249:South Africa
211:granodiorite
169:granodiorite
162:country rock
104:
92:
88:
84:
83:
24:Igneous rock
22:
395:Bundelkhand
351:, south of
349:SlÀttemossa
340:Savitaipale
307:Kaiteriteri
264:Proterozoic
255:Namaqualand
180:plagioclase
166:porphyritic
141:, Northern
127:Occurrences
47:Composition
714:2019-10-16
679:2019-06-30
615:. Struik.
590:. Struik.
554:January 8,
541:(1): 104.
514:2115/36063
402:References
353:JĂ€rnforsen
242:k-feldspar
227:Ordovician
213:exists at
204:K-feldspar
113:spheroidal
93:orbiculite
452:129709727
375:, Ireland
357:Hultsfred
289:Concordia
217:south of
196:magnetite
184:amphibole
158:batholith
155:tonalitic
111:layered,
105:orbicules
825:Category
741:29 March
643:29 March
393:Pichor,
383:Portugal
326:Zimbabwe
147:Jurassic
101:granitic
53:Granitic
831:Granite
776:Bibcode
432:Bibcode
344:Finland
317:Finland
253:In the
238:Miocene
234:Chaitén
192:biotite
139:Caldera
121:Finland
639:. 1914
619:
594:
450:
361:Sweden
223:pluton
200:quartz
172:matrix
732:(PDF)
448:S2CID
143:Chile
132:Chile
743:2017
645:2017
617:ISBN
592:ISBN
556:2018
313:Kuru
194:and
182:and
151:dyke
784:doi
543:doi
510:hdl
440:doi
428:143
91:or
827::
811:70
809:.
805:.
782:.
772:90
770:.
734:.
707:.
672:.
539:45
531:.
506:17
504:.
475:70
473:.
469:.
446:.
438:.
426:.
422:.
410:^
381:,
359:,
355:,
342:,
333:,
324:,
315:,
305:,
291:,
190:,
107:-
790:.
786::
778::
745:.
717:.
682:.
647:.
625:.
600:.
558:.
545::
516:.
512::
454:.
442::
434::
229:.
80:.
68:.
41:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
