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Fossil plants preserved in detail by mineral infiltration are especially valued by paleobotanists because they preserve details of uncompacted form and cellular detail not found in plant impressions and compressions. The most informative kind of fossil is permineralization, in which the minerals fill cell cavities and conserve the original cell walls of the plant. Less useful are remains that are petrified, literally turned into stone, because even the cell walls are replaced by mineral. In Oregon, permineralized and petrified wood is generally preserved by silica derived from the alteration of volcanic rocks. In Ohio through Iowa another form of permineralized plant is found within coal seams, preserved by calcite in nodules colloquially called "coal balls". In black shales, plant material is permineralized by pyrite, again with preservation of microscopic details. These specimens were collected by Professor Retallack during his career as a paleobotanist. Photography by Win McLaughlin, text by Greg Retallack, and web development by Keith Hamm. Images © UO Museum of Natural and Cultural History. Production of this gallery was generously supported by The Ford Family Foundation.

Callixylon whiteanum, Progymnosperm trunk
1 of 15
Diaphorodendron scleroticum, Lycopsid stems
2 of 15
Psaronius brasiliensis, Tree fern trunk
3 of 15
Palaeosmunda playfordi, Tree fern apex
4 of 15
Rhexoxylon africanum, Corystosperm trunk
5 of 15
Araucarioxylon arizonicum, Conifer trunk
6 of 15
Araucaria mirabilis, Conifer cone
7 of 15
Pararaucaria patagonica, Conifer cone
8 of 15
Agathis sp., Conifer stem
9 of 15
Nypa burtini, Palm nut
10 of 15
Palaeophytocrene foveolata, Icacina vine fruit stone
11 of 15
Coryloides hancocki, Hazel nut
12 of 15
Ensete oregonense, Banana seed
13 of 15
Iodicarpa ampla, Icacina vine fruit stone
14 of 15
Quercus sp., Oak wood
15 of 15