Is there shungite not from Karelia?
Short answer – no. But let’s get into details.
Lately we have been receiving a lot of questions about different sources of shungite outside of Karelia and even specimens of so-called «shungites» from Colombia, Brazil and other locations. Let’s figure out together if there is non-Karelian shungite.
First time the name was used by Dr. Alexander Inostrantsev in 1879. He defined it as a natural non-crystalline non-coal carbon from Shunga village, Karelia – we know it now under the name of noble (silver) shungite. Lately it has been used to describe all carbon bearing rocks of the extensive Lake Onega region, with the different types of shungite distinguished by their carbon contents (starting from 20-30% of carbon). Despite the strong opinions of many people who have studied shungite there is still no consensus about its origin. But what we know for sure because of its isotopic composition, is that source of the carbon is biogenic. Shungite could be either metamorphized under high temperature (associated with volcanic activity) petroleum or coal.
Photo made in the historical Petrovskaya shungite mine.
There are a lot of carbon-rich rocks around the globe – the most common are black (carboniferous) shales, usually associated with pyrite and quartz. For a geologist they seem quite conductive and have high carbon grade, but only comparing to other rocks. Usually black shale has resistivity more than 50 000 Om per m, while shungite has it less than 0,001 Om per m. It means, using multimeter you’ll probably see infinite or few thousand kilo Om resistivity for black shale specimen. Also, black shales have only few percent (rarely up to 3-4%) carbon grade. It seems weird, but only 1% of carbon can make a rock completely black!
Specimens of black shale with pyrite from Brazil ->
Another carbon-rich group of rocks are pyrobitumens – which are simply metamorphized (but usually under lower than shungite temperatures) petroleum. There are numerous occurrences of pyrobitumens in the world and they can be easily confused with noble shungite. Such pyrobitumens can have glassy luster and conchoidal fracture. Usually, pyrobitumens are lighter but the main difference to distinguish pyrobitumen from shungite is its conductivity. The record of conductivity among pyrobitumens is 500 Sm/m, while noble shungite is up to 8000 Sm/m (16 times more!). Specimen from Columbia that we’ve been studying in Russia has conductivity less than 10 Sm/m.
The image on the left shows a multimeter showing zero resistivity for a specimen of noble shungite from Karelia, the image on the right shows a multimeter showing high resistivity for a pyrobitumen specimen from Columbia.
What does it mean? Using multimeter, you’ll probably get resistivity around few Oms for specimen of shungite and dozens of kilo Oms for pyrobitumens. Multimeter is your friend when it comes to shungite! of today, no significant occurrences of shungite outside of Karelia have been reported. Please don’t take anyone’s word, when you see non-Karelian shungite for sale and always be armed with multimeter, while shopping for shungite!