(Reuters) - Benchmark Mineral Intelligence, a UK-based provider of critical minerals pricing and data, said it had bought smaller peer Rho Motion in a deal that will make it one of the world's largest sources of market information for the electric vehicle supply chain.

The transaction, which closed on Monday, is worth roughly $50 million, according a source familiar with the terms. The combined company will have a staff of approximately 250, Benchmark said, and compete with S&P Global, privately held Fastmarkets and others.

Subscription-based Benchmark supplies minerals-related data for miners, battery makers, politicians and others. Rho Motion, founded in 2018, has long focused further downstream in the supply chain, tracking EV sales, battery installations, recycling, rare earth magnet production and related areas.

"Where Benchmark's coverage stops, Rho Motion's starts," said Simon Moores, Benchmark's CEO.

The buyout is Benchmark's first transaction since private equity fund Spectrum Equity bought a 20% stake in the London-based firm last November. That investment valued Benchmark at roughly $500 million at the time.

Rho Motion, which will keep its name and remain based in Britain, said it decided to sell to Benchmark after "a long search for a partner who shares our values."

"The combined expertise of the two companies will provide a complete solution to guide the trillion dollar challenge of building the future energy landscape," said Adam Panayi, Rho Motion's founder and managing director.

While it lost out to rival Fastmarkets in 2019 to provide reference pricing for the London Metal Exchange's lithium contract, Benchmark has since grown rapidly by providing data and pricing to other customers.

(Reporting by Ernest Scheyder; Editing by Jamie Freed)

By Ernest Scheyder