[fred_is_fred]

The Lithos Carbon idea is interesting. The mine they show looks like they can just scrape it rather than needing to mine it with explosives. Unfortunately the site's blog has 1 post and it is 3.5 years old. Is it still a going concern?

[apothegm]

There’s an “in the news” entry on their site from this January (and a skim of the article does find them mentioned), so signs point to yes.