Mariana Minerals, a San Francisco company that develops critical minerals projects using its own software, raised a $310m Series B, announced on 3 August 2026. Khosla Ventures led the round.
Returning investors Andreessen Horowitz and Breakthrough Energy Ventures took part. New investors were Greenoaks, Halo Fund, Pax Ventures, StepStone Group, BHP Ventures, Washington Harbour Partners, Greycroft, General Innovation Capital Partners, Mitsubishi Corporation, In-Q-Tel and Earthshot Ventures, according to the press release.
Mariana did not state a valuation. Dealroom reported it at $1.5bn. The company said it has raised about $400m in parent and project capital to date.
“This additional capital lets us move from proving the model to scaling it”Turner Caldwell, CEO and Co-Founder, Mariana Minerals
What Mariana does
Mariana develops and operates mining and processing projects with MarianaOS, a software platform that combines tools for capital project delivery, plant operation and mine operation in one AI and machine learning stack. The company says this halves the five-to-ten-year timelines typical of such projects.
Dealroom reported that Mariana was founded in 2024 by Turner Caldwell, a former Tesla factory engineer, with Baker Tilney and Juan Lozano. Caldwell is chief executive.
The press release lists three components of MarianaOS: CapitalProjectOS for building projects, PlantOS for processing plants and MineOS for mines.
The projects
Copper One, in south-eastern Utah, was acquired in late 2025. The company said mining there restarted under autonomous orchestration within four months, and it targets 50,000 metric tons of refined copper a year. Dealroom described it as a restarted idled mine.
Lithium One, in East Texas, broke ground in the fourth quarter of 2025. Mariana describes it as the world's first gigawatt-hour-scale facility to produce lithium from oil and gas produced water, with commercial production targeted for the first half of 2027.
The company's long-term goal is 10 commercial-scale projects in 10 years.
Mariana says the long-term target of 10 commercial-scale projects in 10 years will be met by running each project on MarianaOS.
Who invested
Vinod Khosla, founder of Khosla Ventures, said the minerals are there and that what has been missing is the will and the AI to run mining and refining autonomously.
Dealroom noted that Andreessen Horowitz is a longtime backer. The sources did not give the amounts or dates of earlier rounds.
What the money is for
Mariana said the Series B will expand its project portfolio, build out active projects including Copper One and Lithium One, and deploy MarianaOS further.
Caldwell said the capital lets the company move from proving the model to scaling it. Dealroom quoted him saying the goal is to reduce the cost of core inputs to the modern economy over time.
Employee numbers were not disclosed in either source.
Dealroom's own database lists total funding at $395m, slightly below the $400m given by the company, a difference the article does not explain.
Company website: marianaminerals.com