Petrifactions and Wood-Templated Ceramics: Comparisons Between Natural and Artificial Silicification

Abstract

Fascination with petrified wood has stimulated interest in understanding the process of natural petrifaction. Early attempts of modeling natural petrifaction in the laboratory have been limited to mimicking incipient permineralization resulting in the creation of silica casts of pore spaces and inner cell walls. Silica lithomorphs produced through artificial silicification provided a possible avenue for studying microstructure of wood. More recently artificial petrifaction is motivated by the goal of creating advanced ceramic materials for engineering applications. The concept of using wood as a biotemplate has led to the creation of porous ceramics by cell wall replacement. To some extent artificial and natural petrifaction processes are comparable; although, some of the materials and procedures used in the laboratory are not found in nature. Research focused on the composition and structure of fossil wood from different-aged deposits is compared with research focused on the development of wood-templated porous ceramics. Differences and similarities in the pathways of natural silicification and creation of biomorphous ceramics are discussed. The comparison between artificial and natural silicification highlights the particular significance of the degree to which (de)lignification is needed for silica permeation.

Wood Petrifaction: A New View of Permineralization and Replacement

“…A comprehensive overview of these experiments appears in a recent article [28]. Several basic strategies have been employed, the simplest approach being to infiltrate silica-bearing solutions into permeable wood, often using elevated temperatures to speed the rate of silica precipitation.…”

“…Despite these experimental variations, the initial steps in these processes all involve permineralization, where silica precipitates in open spaces within the intact wood ( Figure 13). to use wood as a template for deposition of ceramic materials such as silicon carbide [28][29][30][31], or zeolites [32]. The goal of these studies has been to achieve porous materials that have industrial value, rather than to duplicate natural silicification.…”

Multi-Stage Silicification of Pliocene Wood: Re-Examination of an 1895 Discovery from Idaho, USA

“…This concept has been incorporated into every silicification model that has since been proposed. Dietrich et al provide a review of studies on artificial and natural silicification [55]. More recently, Mustoe [56] studied the evidence of multiple silicification pathways of Neogene fossil woods.…”

A Silicified Carboniferous Lycopsid Forest in the Colorado Rocky Mountains, USA

“…A second possibility is that the cell walls are mineralized with amorphous opal (opal-A). The Lower Pennsylvanian age of the deposit makes an opaline composition unlikely, because opal-A transforms relatively rapidly to opal-CT, and from there to quartz; opalized wood is common in Cenozoic formations, but virtually unknown in older deposits [21]. We prefer the third interpretation, which is that the cell walls appear to be isotropic because they consist of aggregates of extremely small quartz particles.…”