Hadean zircon from a 3.3 Ga sandstone, Barberton greenstone belt, South Africa

Hadean zircons hold the promise of providing a rare window into the crustal development and surface evolution of early Earth. To date, the only known sources of abundant Hadean zircons are sedimentary units in the Jack Hills and Mount Narryer regions of Western Australia. Here we describe a sedimentary layer, termed the Green Sandstone Bed, dated at ca. 3306 Ma, in the Barberton greenstone belt, South Africa, that contains abundant zircons ranging from 3300 to 4100 Ma, many of which predate the oldest known rocks in the greenstone belt at ca. 3550 Ma. This adds to a very small number of known Hadean zircon-bearing localities and is particularly important due to its low degree of thermal metamorphism (lower greenschist facies) and negligible strain. There is a high probability that primary mineral compositions of zircon and other heavy minerals present in this bed are well preserved.