Leonardo DiCaprio liked the lab-created diamonds from Bay Area firm Diamond Foundry so much, he invested in the company.

The “Blood Diamond” movie star has touted the company for “cultivating real diamonds in America without the human and environmental toll of mining.” Its gems come from a “plasma reactor” and not from the Earth.

CEO Martin Roscheisen said the rocks from his firm — headquartered in San Carlos with a foundry in South San Francisco — are made in a way that replicates natural processes, and are indistinguishable from the real thing. He said they end up costing about 10 percent less than diamonds mined from the Earth because people can buy them directly from Diamond Foundry.

Roscheisen was a founder of San Jose’s Nanosolar, which crashed and burned in 2013 when the solar panel industry declined. He and his Nanosolar engineering team then pivoted into cultivated diamonds, using techniques similar to those used for making semiconductors and solar-power cells.

“We gained a lot of experience in high-tech manufacturing — basically we got an education worth $640 million in solar. So when we set out to do diamonds, we made sure we’d be able to nail it,” he said.

Roscheisen recently chatted with this newspaper about the business of cultivated diamonds and his firm’s high-tech method of manufacture. His remarks have been edited for length and clarity.

Q How long does it take to make a one-carat diamond in your lab?

A It takes approximately two weeks to grow a one-carat diamond. This is actually the same length of time that Earth takes to form a diamond — in a sense not surprising as the chemistry and physics is the same. It’s a process that builds the diamond lattice atom by atom in a reactor that creates a “sun on Earth” plasma with very high temperature. The key science behind our reactor design was just discovered three years ago. Many people believe it takes Earth millions of years to form a diamond — but the truth is that diamond forms relatively fast inside Earth; then the formed diamond just sits there buried in the soil for a possibly long period of time.

Q How many diamonds do you produce per month or year?

A We are the largest diamond producer in America, with a monthly production of 4,000 carats per month. Each production batch sells out very quickly — within two to three weeks.

Q How does the diamond quality from Diamond Foundry compare to diamonds from the Earth, i.e. can you make flawless ones?

A We can control the quality down to the atomic level. Right now our baseline production process yields a distribution of qualities that matches fairly exactly the demand in the U.S.

Q How did you get from the solar industry to cultivated diamonds?

A We could not make solar cell manufacturing profitable. With diamonds being 500 times as valuable as gold, we believe we can make that profitable.

Q Is Diamond Foundry profitable?

A We are on track to be profitable this year. Right now, we are investing heavily, so burning more capital than we make.

Q How do you assign a value to a particular diamond?

A There’s a $30 billion market for diamonds. It’s a commodity traded at exchanges. We price according to these market prices. The value of a diamond is supply meeting demand.

Q How do you convince consumers that a Diamond Foundry lab-made diamond is as precious as one that’s dug from the Earth?

A If you ask people abstractly “whether they would buy a synthetic diamond,” people tend to be disinclined. But that’s like asking someone in 1990 whether they would buy an electric car, at a time when the only electric cars in existence were golf carts. When people see our diamonds in a store and understand their cultivation, there is zero resistance. We lose virtually no customer once they are educated.

Q The diamond industry, even after changes in the wake of outrage over “blood diamonds,” still has severe social and environmental downsides — is there a social/environmental impact aspect to Diamond Foundry’s work?

A Yes, of course. A lot of our investors want to make a positive difference. Mining has an environmental and social imprint unlike any other human activity. It happens at a vast, un-human industrial scale. There is nothing romantic about mining. There are 3 million slaves digging for diamonds in Africa, and in India, the small diamonds are polished “up in the villages,” a euphemism for child labor.

Q Has DiCaprio’s involvement in the company drawn interest from other celebrities who might want to wear your diamonds, and has his involvement drawn interest in Diamond Foundry from the general public?

A Yes on all. We now have additional top celebrities as investors and will launch special events in 2017.

Q What effects do you expect Diamond Foundry will cause in the diamond industry as a whole, and what effects would you like to see Diamond Foundry cause in the market for diamonds?

A In 20 years, 100 percent of all diamonds will be man-made because there’s no Earth supply left by then, according to the large miners. There’s been no new mine discovered in 25 years.