"Scurfield and Segnit had reported that the petrification of wood can be considered to take place in five stages.
"1. Entry of silica in solution or as a colloid into the wood.
2. Penetration of silica into the cell walls of the wood's structure.
3. Progressive dissolving of the cell walls which are at the same time replaced by silica so that the wood's dimensional stability is maintained.
4. Silica deposition within the voids within the cellular wall framework structure.
5. Final hardening (lithification) by Drying out."
"Furthermore Oehler had previously shown that the silica minerals quartz and chalcedony critically important in the petrification of wood, can be made, rapidly in the laboratory from silica gel. At 300°C (572°F) and 3 kilobars (about 3,000 atmospheres) pressure only 25 hours was required to crystallize quartz, whereas at only 165°C (329°F) and 3 kilobars pressure the same degree of crystallization occurred in 170 hours (about seven days)."