"Wood crystals"    Part 1
deutsche Version

This is not about quartz crystals in silicified wood, which is a common phenomenon, but about wood preserved within quartz crystals, which apparently had never been noticed before. A monograph [1] listing all inclusions seen in quartz crystals does not mention wood tissue. One may wonder why but there is a possible explanation: The inlusions had been found by mineral collectors mainly interested in crystals of cm-size and above. If they look at crystals of mm-size and below, then for the arrangement of crystal faces but not for the "dirt" enclosed. Also they probably never inspected the tiny quartz crystals often seen in silicified wood. This may explain why pictures like Fig.1 have been perceived as stunning, also by R. Rykart, the author of the Quartz Monograph [1].
wood cells preserved in quartz crystal
                                            Fig.1 (right): A small part of coniferous wood preserved within a quartz crystal. Width of the crystal 0.8mm.
wood in quartz crystal in fossil wood
Fig.2 (left): Silicified coniferous-type wood cross section with quartz crystal
with traces of wood preserved within. Width of the crystal 0.6 mm.

The particular aspect of the specimens in Figs.1,2, where the crystal axis coincides with the wood axis, and with wood confined to the centre, is not typical for the phenomenon. Apparently, wood inside crystals is more easily discovered in such cases where the cut is perpendicular to the tracheids, and if the cut is perpendicular to the crystal axis, too, it is all the more conspicuous.
Quartz crystal sections with less regular shape but with wood throughout are seen in Fig.3. 
wood in quartz

Fig.3 (right):  Coniferous wood preserved within quartz crystals in fossil wood. Width of the picture 2mm.

Judging from the equal orientation of the wood in the quartz grains in Fig.3 one can conclude that the whole is not a heap of petrified wood fragments but crystals grown within the wood while the wood was still coherent. They must have grown through the wood without hindrance as if the wood were not there, which indicates that the wood substance had already been essentially dissolved but the dark decay products were still arranged in their original position, probably in silica gel, so that the overall wood structure was still visible and became incorporated into the crystals and safely preserved there.
Since quartz crystals are more resistant to dissolution than chalcedony, it appears that the most suitable place for the persistence of a fossil structure is inside a quartz crystal.

Apparently, these pictures show the first fossils discovered inside crystals. It seems worth while looking for fossils other than wood making use of this safe means of preservation.

"Wood crystals" had been first published in 1999 [2] although the phenomenon is widespread and could well have been discovered in times when fossil wood was first inspected with a microscope. Apparently the palaeontologists did not expect the like and therefore did not closely look at the crystals, possibly under the influence of the scholastic subdivision of Nature into mineral kingdom, plant kingdom, and animal kingdom, considered naive now, which made them ignore the crystals since they did not belong to their two kingdoms of interest. As an exception to such attitude, H. Huhle looked for and found Tertiary wood inside quartz cystals [3].

The present samples had been found among gravel near the Kyffhäuser Mountains, Germany, uppermost Carboniferous [4],
and provided by W.+G. Etzrodt, Borxleben.

Sample labels: Fig.1: KyB/48.2,  Fig.2: KyB/24.2,  Fig.3: KyB/38.1

H.-J. Weiss
    2011,   emended 2016

[1]  R. Rykart: Quarz-Monographie, Ott Verlag Thun, 1989
[2]  H.-J. Weiss, R. Noll: "Holzkristalle". Veröff. Mus. Naturk. Chemnitz 22(1999), 57-64.
[3]  H. Huhle: Holz im Quarz. Veröff. Mus. Naturk. Chemnitz 27(2004), 123-24.
[4]  J. Schneider, R. Rößler, B. Gaitsch: Stratigraphy and facies of the Middle European continental Carboniferous and Permian excursion guide A5, 1995.
quartz crystal with wood inside
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