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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 alternate with bands or lenticles in which minerals having flaky or elongate prismatic habits predominate. 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., granite gneiss, orthogneiss, paragneiss).


Unique IdentifiersHide

Mindat ID:
48629
Long-form identifier:
mindat:1:1:48629:7
GUID
(UUID V4):
bd8c270e-7b2d-4261-8c32-52d69ffa8ef5

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:
Amphibole(Na, K, β—»)(Ca,Na)2(Mg,Fe,Al)5((Si,Al)8O22)(OH,F,Cl,O)2
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:
Neochaotian to Devonian : ~4600 Ma to 358.9 Β± 0.4 Ma - based on 11 recorded ages.

Other Language Names for GneissHide

German:Gneis
Irish Gaelic:Naghas

Varieties of GneissHide

Schisty gneissA gneiss with a distinct schistosity.

Common AssociatesHide

Associated Minerals Based on Photo Data:
6 photos of Gneiss associated with Garnet GroupX3Z2(SiO4)3
4 photos of Gneiss associated with AlmandineFe2+3Al2(SiO4)3
4 photos of Gneiss associated with QuartzSiO2
4 photos of Gneiss associated with Plagioclase(Na,Ca)[(Si,Al)AlSi2]O8
4 photos of Gneiss associated with BiotiteK(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2
3 photos of Gneiss associated with Cordierite(Mg,Fe)2Al3(AlSi5O18)
3 photos of Gneiss associated with SillimaniteAl2(SiO4)O
2 photos of Gneiss associated with RubyAl2O3
1 photo of Gneiss associated with HΓΈgtuvaiteCa4[Fe2+6Fe3+6]O4[Si8Be2Al2O36]
1 photo of Gneiss associated with Eclogite

Internet Links for GneissHide

References for GneissHide

Reference List:

Localities for GneissHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListShow

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