It's vein graphite The only current source is the Sri Lankan mines and they are sold out of product and not providing price quotations to the market at the moment (as Caldude posted here previously).
It sells from $8000 to $10000 per ton
https://www.resourceinvestor.com/2012/05/24/only-a-few-graphite-companies-will-win-mickey-fulp?ref=hp
It's very pure as is inferred from this
“The Li-ion batteries were assembled using the sol-gel synthesized cathode materials, natural untreated vein graphite of Sri Lanka as the anode material and 1 M LiPF6 in EC/DMC as liquid electrolyte, and their performances were tested.”
From https://www.sljol.info/index.php/SLJP/article/view/213