FMF - Friends of Minerals Forum, discussion and message board

[marco campos-venuti]

About the relationship between mineralogy and biology I recently published a voluminous book entitled "Biominerals: Microbial Life in Agates and other Minerals". In this work I try to identify structures of biological origin in hundreds of mineral samples that would normally be placed in mineral showcases. The results indicate that biomineral structures are much more common than we might imagine.
You can find the book here:
https://www.agatesandjaspers.com/
(link normalized by FMF)
528 pages, +1000 figures, 78 diagrams

[James Catmur]

I like the Cotham marble

[Roger Warin]

I have everything to learn in this area.
What is the mechanism that initiates this type of biomineral growth?
I only know (but am only an amateur) one mineral of bacterial origin. Gold scales.
I believe that these bacteria play the role of a mineralizing agent that patiently concentrates the highly disseminated gold in the rocks. They would play a parallel role to classical agents, such as selenides and tellurides.

[James Catmur]

Try reading this for Cotham marble

https://www.wikiwand.com/en/Cotham_Marble

James

[marco campos-venuti]

Hi Roger,
I am a geologist and I had to document myself to do an interdisciplinary work between geology and biology. This is why I added an initial chapter to the book to explain the basic concepts to the less experienced. Despite there is an extensive literature on extremophile bacteria, there is almost nothing written about the relationship between their biomineralizing activity and mineral structures known to mineralogists. And my book tries to identify these structures.
In practice, bacteria breathe by exploiting the energy of redox reactions that are often already active in the surrounding environment. The outer surface of the bacterium has a mucous gel which becomes negatively charged and which therefore attracts positive metal ions. The oxidation or reduction of these ions allows the bacterium to obtain energy, but indirectly precipitates oxides, sulfides or other minerals. Many pseudofossils such as dendrites and moss agates are actually true fossils, or at least fossil tracks that we can call microbialites, of which stromatolites are a type that forms with the collaboration of cyanobacteria, i.e. under sunlight. Microbalites form in many environments of the deep biosphere and are associated with common minerals such as agate, malachite, rhodochrosite, sphalerite, as well as gold, silver and copper.

[marco campos-venuti]

Hi James,
Cotham Marble is a well-known and well-studied stromatolite with dendritic-plumy shapes. The second photo of the cover represents a manganese dendrite, which I theorize precipitated from a colony of bacteria in an epigenetic crevice. The third photo represents a plume agate with structures that recall those of living bacterial colonies and which again I theorize are biomineralized by bacteria. The last photo is a feather malachite. All four samples repeat the same geometric pattern with the growth of dendritic-plumy structures starting from a linear biofilm.