Figure 8.7   The oldest fossils on Earth? A mass of thin thread-like fi laments found in a massive sulfi de deposit in Western Australia dated at 3.2 Ga. The fact the threads occur in loose groups and in tight masses, and that they are not oriented in one direction, suggests they are organic. The fi laments are lined with minute specks of pyrite, showing black, encased in chert. Field of view is 250 Ám across. (Courtesy of Birger Rasmussen.)

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