What are some of the oldest rocks so far discovered on Earth?

 What are some of the oldest rocks so far discovered on Earth?

Scientists have found rocks exceeding 3.5 billion years of age on all the Earth's continents. But the oldest rocks uncovered so far are the Acasta Gneisses in north 

western Canada near Creat Slave Lake, which has been dated at about 4.03 billion years old. Others that are not as old include the lsua Supracrustal rocks in West Greenland (3.7 to 3.8 billion years old), rocks from the Minnesota River Valley and northern Michigan (3.5 to 3.7 billion years old), rocks in Swaziland (3.4 to 3.5 billion years old), and rocks from western Australia (3.4 to 3.6 billion years old). These ancient rocks are mostly from lava flows and shallow water sedimentary processes. This seems to indicate that they were not from the original crust, but formed afterward.

The oldest materials found on Earth to date are tiny, single zircon crystals uncovered in younger sedimentary layers of rock. These crystals, found in western Australia, have been dated at 4.3 billion years old, but the source of the crystals has not yet been discovered.