What is the oldest rock in the world?
gneiss
basalt
quartzite
syenite
The Acasta Gneiss in the Canadian Shield in the Northwest Territories, Canada is composed of the Archaean igneous and gneissic cores of ancient mountain chains that have been exposed in a glacial peneplain. Analyses of zircons from a felsic orthogneiss with presumed granitic protolith returned an age of 4.031 ±0.003 Ga.  
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Answers by country
gneiss
basalt
quartzite
syenite
answers
 Australia
Australia20
 Greece
Greece15
 India
India43
 Germany
Germany103
 Poland
Poland1668
 the United States
the United States86
 the United Kingdom
the United Kingdom34
 Austria
Austria13
 Republic of Ireland
Republic of Ireland12