GR Engineering Services was awarded preferred tenderer status for the design and construction of the processing and paste fill plants.

The contract will be a fixed price engineering procurement and construction contract, with design expected to begin in the June quarter, followed by construction in the December quarter.

Contracts for the power station and distribution and the bulk earthworks are still to be awarded.

It comes as all aspects of the $A443 million Nova development remain on or ahead schedule.

The box cut has reached 22m depth and is now in fresh rock, with the establishment of the portal and start of the underground decline on track for the last week of April.

Underground mining equipment has arrived on site for the start of the decline.

Construction of the tailings dam, infrastructure corridors and accommodation village are underway.

Meanwhile, Sirius is continuing exploration while Nova is being built.

Further diamond drilling at the Baloo gold discovery returned 1.1m at 9.74 grams per tonne gold from 20.6m; 29.8m at 2.17gpt gold from 33.7m; and 13.3m at 1.75gpt gold from 15.5m, including 3m at 4.51gpt gold.

GMP Securities analyst Duncan Hughes said the results had reduced the likelihood of extensive primary mineralisation at Baloo as well as the potential for a substantial standalone operation.

"There are another nine diamond holes that await assays from the fresh rock to be returned and there is still every chance that these may define primary gold mineralisation at more encouraging widths and grades," he said this morning.

"But at this stage the depth extent looks somewhat limited."

Results for the further holes are pending and three diamond rigs are testing the extent and nature of the primary gold mineralisation, while a reverse circulation rig is replicating the original aircore drilling as a basis for a JORC oxide resource.

The oxide zone has been defined over 750m with the most recent results including 11m at 1.38gpt gold from 4m; 2m at 9.67gpt gold from 26m; and 10m at 1.64gpt gold from 13m, including 1m at 12.4gpt gold.

Sirius also hit high-grade gold at Monsoon, including 12m at 16.9gpt gold from 68m, and 12m at 1.34gpt gold from 20m, including 4m at 3.29gpt gold.

On the nickel front, the first four diamond holes at the Crux nickel intrusion returned 7m at 0.3% nickel from 448m, and 8.2m at 0.26% nickel and 9.7% chromium oxide from 111.8m.

Of the 11 holes completed, downhole electromagnetics have been completed on eight with no conductors identified, though the work to date has only covered 2% of the target area.

Shares in Sirius slumped 6.5% to $2.70 after a 3% slump in the nickel price on Friday.