This tree trunk from Wikipedia has been turned to stone somehow. It was composed of organic materials but now consists entirely of inorganic substances, mostly silicates.
Much of the original details have been preserved. The rings are visible along with radial cracks and in other pictures we can easily distinguish the different textures of bark and.

How does this happen?

According to Wikipedia the tree was first submerged in water to prevent it from decaying and then over many years the organic matter was replaced by dissolved minerals in the water by a process of sedimentation.

So the new material has seeped into the cellular interior whilst the cell wall is still intact enough to shape the mineral deposits correctly by acting as a mould. The article mentions that the decay of cellulose must precisely match the rate of mineral deposits for the process to work properly.

Girolamo Segato (1792-1836) was an Italian embalmer who produced apparently similar results within his own lifetime by unknown means.

Shown below, a foetus, a kidney and a table made from petrified organs made as a present for Grand Duke Ferdinand III who was not amused.

Efisio Marini (1835-1900) also produced petrified remains by means of an ‘unidentified mix of mineral substances, again without the need to cut or damage the body parts.

A concretion is a hard, compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur – Wikipedia

Sizes can vary from a few millimetres to a few metres and the contents can vary from crystalline minerals to organic life forms.

A concretion will often consist of an outer shell surrounding a cavity which in turn contains as its ‘nucleus’ a petrified organism, preserved with remarkable detail as seen here with a mineralised crab.

The facts that so much detail is preserved and so much of the original material is present suggest that fossilisation happened relatively quickly, before the organism had time to decay.

Here we have a fish apparently preserved in the act of swallowing another fish taken from the video by Peter Mungo Jupp.

This and other similar fossils of creatures petrified in the act of giving birth lend some support to claims that death was instantaneous and it, along with the petrifaction, was caused by a sudden exposure to a powerful energetic current of some sort and that the fossilisation is not by the slow deposits of minerals but a sudden transmutation of elements.

Hidekazu Yoshida and a team of Japanese scientists made a thorough investigation of this phenomenon and found that under certain conditions the breakdown of the organism created very specific chemical reactions and physical channels that pretty much turned the decaying matter into a self-petrification factory.

The process of mineralisation is now not a random process depending upon slow diffusion of salts into biological matter but an organised system of reactions that can form a fossil many times faster than previously thought, maybe only in a matter of months.

How old are fossils? Fossils do not need thousands of ears to form and so this now calls into question the dating processes from sedimentary rocks and suggests that the actual age of the fossils now may have been miscalculated. [Paper]

Related pages:

Peter Mungo Jupp: Instant Fossilization | EU2017

Girolamo Segato

Girolamo Segato and Efisio Marini: the Petrifiers of Bodies

Bodies of stone: Girolamo Segato (1792-1836).

Experimental Supporting Evidence – Lattice Confinement Fusion Reactions & the Sun! – Pierre-Marie Robitaille

Synthesis and transmutation of stable and radioactive isotopes in biological systems – Kornilova, Vysotskii

Generalized conditions of spherical carbonate concretion formation around decaying organic matter in early diagenesis – Yoshida et al

Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores – Yoshida et al

Authors: Evan Saitta, Tom Kaye, Jakob Vinther