Core Lithium, which officially cut the ribbon to mark the start of mining at Finniss yesterday, announced the A$60 million, five-year contract at the same time.
The new deal is focused on operation of the dense media separation plant that is Primero is constructing and is set to be commissioned next year.
It also covers the tailings storage facility.
NRW chief executive Jules Pemberton said Primero was successfully diversifying into longer term operational contracts.
Core has an option to extend the contract beyond the initial term.
Primero has a long history in Western Australia's lithium space, working with Pilbara Minerals' Pilgangoora, Covalent Lithium's Mt Holland, Allkem's Mt Cattlin, and Alita Resources' Bald Hill developments.
Core's $89 million Finniss is Australia's only lithium mine outside Western Australia. It started
selling direct shipping ore this month, and expects to sell its first spodumene concentrate next year.
Finniss has transformed from an exploration concept to open pit mine in just over six years and is expected to process some 16 million tonnes of ore over 12 years.
Core, which now has cash of around $210 million, expects to spend a further $95 million to produce its first concentrate.
It has earmarked $25 million for extensional and exploration drilling
Core will develop multiple deposits at Finniss to produce 197,000tpa of concentrate for sales to the likes of Ganfeng Lithium and Tesla, with around 80% of production under contract.
Core shares closed yesterday at $1.14, valuing it at $2.1 billion, while NRW's stock was last traded at $2.47, capitalising it at $1.1 billion.