Petrified wood cross section, USA (Arizona), Triassic period (225 million years ago), on custom-made base, 39 x 34 cm

Conifers appeared 230 million years ago on the North American continent, which was a warm and humid area at the time. The sublime colours of this fossil are produced by the elements present in the soil at the time of its fossilization: iron oxide for the red, manganese oxide for the black, and sulphur for the yellow.