The funding from Taurus is being augmented by a $95 million loan to be provided by the federal government, with total project capital of $463 million estimated to be needed.
GR is expected to get to work on the ground in the second quarter of next year, with the engineering firm being given two years or so to get the 7.5 million tonne per annum project into operation.
Thunderbird is promoted by its owner as "one of the most significant zircon discoveries in the past 30 years".
While getting a fix on how profitable the project could be is difficult given the amount of variables at play, the company's bankable feasibility study 18 months ago pointed to earnings of $5.1 billion over a 42-year operation life (on an EBITDA basis).
Sheffield has also pointed at revenue to cost ratio of two-to-one.
Sheffield had cash of $13.7 million at the start of the current quarter.
Shares in Sheffield were up 5% to 84c in morning trade, capitalising the company at $189 million.
The stock recently hit a 12-month high of $1.27.