<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (June 2012) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (June 2012) (Learn how and when to remove this template message) </Td> </Tr> <P> The oldest dated rocks on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history . Such rocks are exposed on the Earth's surface in very few places . Some of the oldest surface rock can be found in the Canadian Shield, Australia, Africa and in a few other old regions around the world . The ages of these felsic rocks are generally between 2.5 and 3.8 billion years . The approximate ages have a margin of error of millions of years . In 1999, the oldest known rock on Earth was dated to 4.031 ± 0.003 billion years, and is part of the Acasta Gneiss of the Slave craton in northwestern Canada . Researchers at McGill University found a rock with a very old model age for extraction from the mantle (3.8 to 4.28 billion years ago) in the Nuvvuagittuq greenstone belt on the coast of Hudson Bay, in northern Quebec; the true age of these samples is still under debate, and they may actually be closer to 3.8 billion years old . Older than these rocks are crystals of the mineral zircon, which can survive the disaggregation of their parent rock and be found and dated in younger rock formations . </P> <P> The oldest material of terrestrial origin that has been dated is a zircon mineral of 4.404 ± 0.008 Ga enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia . The 4.404 ± 0.008 Ga zircon is a slight outlier, with the oldest consistently - dated zircon falling closer to 4.35 Ga . This zircon is part of a population of zircons within the metamorphosed conglomerate, which is believed to have been deposited about 3.060 Ga, which is the age of the youngest detrital zircon in the rock . Recent developments in atom - probe tomography have led to a further constraint on the age of the oldest continental zircon, with the most recent age quoted as 4.374 Ga ± 0.006 . </P>

Of what type are the oldest surviving rocks on earth