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Gneiss

A rock classification type
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About GneissHide

A medium- to high-grade metamorphic rock that commonly has a banded structure and is generally medium- to coarse-grained with poorly developed schistosity.
A foliated rock formed by regional metamorphism, in which bands or lenticles of granular minerals (mostly quartz and feldspars) alternate with bands or lenticles in which minerals having flaky or elongate prismatic habits predominate (typically micas and amphiboles). Generally, less than 50% of the minerals show preferred parallel orientation. Although a gneiss is commonly feldspar- and quartz-rich, the mineral composition is not an essential factor in its definition. Varieties are distinguished by texture (e.g., augen gneiss), characteristic minerals (e.g., hornblende gneiss), or general composition and/or origins (e.g., granitic gneiss, orthogneiss, paragneiss).

The pronunciation is variable, see: https://www.mindat.org/mesg-676000.html but Jolyon’s recording below is probably the most common.


Unique IdentifiersHide

Mindat ID:
48629
Long-form identifier:
mindat:1:1:48629:7

Classification of GneissHide

Sub-divisions of GneissHide

Mineralogy of GneissHide

Non-essential minerals - these minerals are common, sometimes major components, but are not always present:
AmphiboleA petrological term for Amphibole Supergroup.
FeldsparA petrological term for Feldspar Group.
MicaA petrological term for Mica Group.
Silica > QuartzSiO2

Pronunciation of GneissHide

Pronunciation:
PlayRecorded byCountry
Jolyon RalphUnited Kingdom

Age distributionHide

Recorded ages:
to Devonian : 18100 Ma to 358.9 ± 0.4 Ma - based on 27 recorded ages.
Sample ages:
Sample IDRecorded ageGeologic TimeDating method
1419.2 ± 3.2 to 358.9 ± 0.4 MaDevonian
2486 ± 24 MaFurongianRb-Sr whole rock
3~800 MaTonian
42762 ± 200 MaNeoarchean
54000 to 2500 MaArchean
64000 to 2500 MaArchean
74000 to 2500 MaArchean
84000 to 2500 MaArchean
94000 to 2500 MaArchean
104000 to 2500 MaArchean
114000 to 2500 MaArchean
124000 to 2500 MaArchean
134000 to 2500 MaArchean
144000 to 2500 MaArchean
15~4600 to 541 ± 1.0 MaPrecambrian
16~4600 to 541 ± 1.0 MaPrecambrian
17~4600 to 541 ± 1.0 MaPrecambrian
18~4600 to 541 ± 1.0 MaPrecambrian
19~4600 to 541 ± 1.0 MaPrecambrian
20~4600 to 541 ± 1.0 MaPrecambrian
Sample references:
IDLocalityReferenceNotes
1Lizard Complex, Cornwall, England, UK
2Galiñeiro Complex, Vincios, Gondomar, Pontevedra, Galicia, Spain
3Andakatany Deposit, Andakatany, Manandriana District, Amoron'i Mania, Madagascar
4Bhurpidungri, Jharsuguda District, Odisha, India
5Tongshi complex, Pingyi County, Linyi, Shandong, China
6Chintalacheruvu, Palnadu District, Andhra Pradesh, India
7Kanakapura, Ramanagara District, Karnataka, India
8Mikkelvik quarry, Karlsøy, Troms og Finnmark, Norway
9Peralimala Intrusion, Kannur District, Kerala, India
10Ambalavayal intrusion, Wayanad district, Kerala, India
11Peralimala Intrusion, Kannur District, Kerala, India
12Ambalavayal intrusion, Wayanad district, Kerala, India
13Samchampi, Samchampi-Samteran alkaline igneous complex, East Karbi Anglong District, Assam, India
14Reddypalle plug, Sri Sathya Sai District, Andhra Pradesh, India
15Nongcharam-Darugiri area, East Garo Hills District, Meghalaya, India
16Koraput gabbro/nepheline syenite, Koraput District, Odisha, India
17Samalpatti carbonatite complex, Krishnagiri District, Tamil Nadu, India
18Purimetla, Prakasam District, Andhra Pradesh, India
19Uppalapadu Pluton, Prakasam District, Andhra Pradesh, India
20Kudangulam dikes, Tirunelveli District, Tamil Nadu, India

Other Language Names for GneissHide

German:Gneis
Irish Gaelic:Naghas

Varieties of GneissHide

AoriteA gneiss in the state of transition to diorite. The name is derived from the greek word άγουρος (áōros), meaning "immature" (Erdmannsdörfer, 1947).

Common AssociatesHide

Associations Based on Photo Data:
23 photos of Gneiss associated with Garnet GroupX3Z2(SiO4)3
11 photos of Gneiss associated with QuartzSiO2
10 photos of Gneiss associated with 'Biotite gneiss'
9 photos of Gneiss associated with BiotiteK(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2
9 photos of Gneiss associated with 'Migmatite'
9 photos of Gneiss associated with 'Migmatite and related rock'
9 photos of Gneiss associated with PyriteFeS2
8 photos of Gneiss associated with 'Paragneiss'
6 photos of Gneiss associated with CalciteCaCO3
6 photos of Gneiss associated with AlmandineFe2+3Al2(SiO4)3

Internet Links for GneissHide

References for GneissHide

Reference List:

Localities for GneissHide

Showing 5,056 localities.

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