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"Trace Fossils" in Garnets ?


Oxytropidoceras

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Tiny tunnels inside garnets appear to be the result of boring 

microorganisms, Public Library of Science, Physorg, August 8, 2018,

https://phys.org/news/2018-08-tiny-tunnels-garnets-result-microorganisms.html

https://eurekalert.org/pub_releases/2018-08/p-tti080118.php

https://cosmosmagazine.com/geoscience/tiny-tunnels-in-gemstones-found-to-be-caused-by-microbes

 

The open-access paper is:

 

Ivarsson M, Skogby H, Phichaikamjornwut B, Bengtson S, 

Siljeström S, Ounchanum P, et al. (2018) Intricate tunnels 

in garnets from soils and river sediments in Thailand – 

Possible endolithic microborings. PLoS ONE 13(8): e0200351. doi.org/10.1371/journal.pone.0200351 

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0200351
 

Yours,


Paul H.

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More likely inclusions of silica or rutile.  Garnet are extremely hard - Mohs 8-8.5.  I'll have to read the papers.  Thanks for sharing, very interesting.

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Interesting, but I would think that in order to penetrate a silica mineral something would have to produce a very strong acid that would be likely to dissolve the organism long before dissolving silica. It is more reasonable to assume that an organism colonized already existing structures within the garnet. As far as hardness goes, on the moh's scale garnet ranges from 6.5 to 7.5 with the garnet varieties containing aluminum in their makeup being the hardest.

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  • 2 weeks later...

I read a few years ago about actual "garnet-ised" body fossils from Ambanja (Madagascar) :); including a coral and a gastropod. Even had the privilege of seeing them at a Fossil/Mineral show in 2013 (sorry don't have any pictures). This link from the GIA website is the only information I can find about the Madagascan garnet pseudomorphs.

Opalised fossils are the best: a wonderful mix between paleontology and mineralogy!

 

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6 hours ago, The Amateur Paleontologist said:

I read a few years ago about actual "garnet-ised" body fossils from Ambanja (Madagascar) :); including a coral and a gastropod. Even had the privilege of seeing them at a Fossil/Mineral show in 2013 (sorry don't have any pictures). This link from the GIA website is the only information I can find about the Madagascan garnet pseudomorphs.

 

See this link please

 

Regards,

 

Ricardo

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I took at quick look at how garnetized fossils were formed. Ordinarily, conditions (heat and pressure) needed to form garnet would destroy any calcareous fossils before they could be replaced. What happened was part of a fossil bearing bed was metamorphosed by a volcanic intrusion. The shell/ body fossil was dissolved and the empty space was filled with polycrystalline garnet.

 

What interesting fossils.

 

 

From GIA.edu:

Figure 1. These coral (left) and gastropod (right) fossils are pseudomorphs in demantoid garnet from Ambanja, Madagascar. The coral measures 1.5 × 1 cm. Photo by Pierre-Yves Chatagnier.

IMG_0494.JPG

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