A review of historical data by Snowden Optiro has allowed a JORC 2012 inferred resource of 42.1 million tonnes grading 0.4% nickel and 0.016% cobalt for a contained 168,400t nickel and 6700t cobalt to be estimated.
CEO Andrew Nesbitt said the resource was a significant foundation to build on.
The project, on the north-western edge of Finland, covers 284sq.km. Ruossakero was first defined in the 1980s.
Preliminary work by RMC has confirmed extensive areas of komatiitic geology, with widespread presence of sulphides within the Archaean-aged host rocks confirmed by a field visit, and intercepts of 0.89% nickel and 3.15% copper that have not been followed up.
The company spend several months completing due diligence before acquiring Ruossakero and the Kola and Hirvikallio lithium projects from Singapore-based Element92 in November.
Consideration for the three licences was the issue of the issue of A$4 million worth of shares priced at 10c each.
RMC has shifted its focus from the large Wowo Gap nickel laterite project in Papua New Guinea towards Finland and Tanzania over the past two years.
It now has eight licences in Tanzania along strike from the Kabanga project that were previously explored by BHP and Albidon, with the company saying there are walk-up drill targets.
RMC recently raised $2.4 million to fund its initial work.
Shares in the explorer were off 11% this morning at 6.8c, valuing it at $36 million.
The stock has traded at 1.5-19c over the past year.