Silicified wood mimicking charcoal
deutsche Version
wood debris silicified
Permian petrified wood characterized as "black and fragile before silicification" as in Fig.1 has been mistaken repeatedly for fossil charcoal. Such mistake has been rejected by means of this very sample [1].

Fig.1: Coniferous-type wood, degraded and fragmented in water, then silicified together with the water.
Picture width 4mm. (Unrelated detail: pits from dissolved calcite above left.)

Whole tree trunks allegedly turning into charcoal was thought to be feasible when some catastrophic event piled trees into a big heap which finally burned like a charcoal kiln [2]. One can do without such absurd constructs of mind since there is no charcoal involved here but black wood only.
The black aspect of this wood must be due to other causes than the black aspect of charcoal is. The wood in Fig.1 could be black because the cell walls were coated with a black microbial layer. Black microbial layers are known from the Rhynie chert where they give an illusion of sclerenchyma with thick cell walls.

A larger contribution to the black aspect comes from an enigmatic stain in the wood tracheids. This stain may vary along the tracheid between light brownish and black, and it may fill the cell partially or completely, as seen in Fig.2. There, the fracture of the softened wood caused a black tracheid to break. Its broken ends are distinctly visible in Fig.2 above right.
silicified wood cut lengthwise

Fig.2: Silicified wood, lengthwise cut tracheids with various fills: light, variable, black; cross-cut ray cells mostly light-coloured. Width 2mm.

Dark fills are also seen in some of the ray cells in Fig.2. Randomly distributed stained tracheids, cut lengthwise in Fig.2, are seen cross-cut in Fig.3 below left.
Conspicuously, the dark fills tend to arrange themselves in radial rows which may fuse laterally into dark areas. (This is also known from Carboniferous wood, see Fossil Wood News 21.) As a peculiar fact, the cell walls, usually black in this sample, are faintly seen as a gray structure in the black areas in Fig.3.

Also conspicuous are the rays, which had remained bright among the black wood.
silicified wood cross-cut

Fig.3 (right): Silicified wood, cross-cut tracheids with various fills: light, variable, black; cross-cut rays light-coloured. Width 2.8mm, same scale as Fig.2.

A rare phenomenon is uncommonly clearly seen here: The white line in Fig.3 below is an "easy crack path". Apparently the adhesion between the cells had been degraded owing to prolonged submersion so that the crack did not have to break cell walls but took the easy path between the cells while propagating through the tissue.

Finally it appears that the charcoal aspect of this sample vanishes with careful inspection, as already stated in [1]. Very probably the same applies to several other cases of black silicified wood offered as fossil charcoal [2-4]. None of the observed features fits to silicified charcoal. (For comparison with fossil charcoal see [5], for example.)

The cause of the black stain remains uncertain here. From the variability of the stain along some tracheids in Fig.2 one may conclude that possibly microbes had been involved that were able to blacken cell walls and spaces.

Sample W/55, found in 1992 during the preparation of the golf course at Wilmsdorf, Doehlen Basin near Dresden, stored in the own collection. Fig.1,3: W/55.2, Fig.2: W/55.3.

H.-J. Weiss     2019
[1]  H.-J. Weiss:   Fossil Wood News 9
[2]  R. Noll, D. Uhl, S. Lausberg : Brandstrukturen an Kieselhölzern der Donnersberg Formation.
      Veröff. Mus. Naturkunde Chemnitz 26 (2003), 63-72.
[3]  R. Rössler : Der versteinerte Wald von Chemnitz. Museum f. Naturkunde Chemnitz, 2001, 179.
[4]  R. Noll, V. Wilde :  Conifers from the „Uplands“ – Petrified wood from Central Germany, 
       in: U. Dernbach, W.D. Tidwell : Secrets of Petrified Plants, D'ORO Publ., 2002, 88-103
[5]  A. Jasper, D. Uhl et al.: Evidence of wildfires in the Late Permian …, Current Science 110 No3 Feb.2016, 419-423.

quartz crystal with wood inside
Fossil Wood News  35

Site map
Fossil Wood News
Silicified wood