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WikiProject Geology (Rated Start-class, Low-importance)
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DYK nomination[edit]

biological from 2 billion[edit] (talk) 18:57, 20 August 2012 (UTC) What life was 98% carbon 2 billion years ago? The stromatolites were alge/limestone? Does a salp, a current carbon sink possibly exist then?

The pure shungite is thought to represent migrated oil that has been metamorphosed, hence the very high carbon content. Mikenorton (talk) 21:10, 20 August 2012 (UTC)

Shungite rock types: slipped classification categories[edit]

The "Terminology" paragraph currently says, "Shungite-bearing rocks have also been classified purely on their carbon content, with Shungite-1 having a carbon content in the range 98-100 weight percent and Shungite-2, -3, -4 and -5 having contents in the ranges 35-80 percent, 20-35 percent, 10-20 percent and less than 10 percent, respectively." (It is referenced with an article from an Elsevier publication with a paywall so I can't check the source.)

So, what d'you call the ore when it's 80-98% carbon? And, is stuff that's 0-10% carbon actually called a type of shungite rock? --Egmonster (talk) 03:40, 4 April 2015 (UTC)

Good question. The quote from the paper is "Borisov (1956) classifies shungite and shungite-bearing rocks by their carbon content. However, his terms, shungite-1 (98–100 wt.% C), shungite-2 (35–80 wt.% C), shungite-3 (20–35 wt. %C), shungite-4 (10–20 wt.% C) and shungite-5 (<10% wt.% C), do not distinguish between shungite and shungite-bearing rocks. Moreover, this widely accepted classification lumps together shungite-bearing rocks, which may have contrasting compositions and lithologies. Shungite-5, for example, may be represented by tuff, dolostone, limestone, chert, basalt or even gabbro." I don't have access to the Borisov publication, so I can only speculate that shungite-bearing rocks range up to a maximum of 80%, whereas the mineral itself is 98% or greater, so no need for a term for 81-97%, but that is a guess. Shungite-5 appears to be anything with a little bit of shungite in it. Mikenorton (talk) 10:16, 4 April 2015 (UTC)
Thank you for checking that this quote matches the proximate source's text. I suppose this absurd distribution could be possible, but it seems more likely that a transcription error has interposed between Borisov and here. A classification derived from Borisov and others, Buseck et al 1997, is referenced by other papers, so one could replace the Elsvier nonsense above with that.--Egmonster (talk) 17:20, 9 November 2015 (UTC)