The new plant is expected to produce 2.2m ton of diamonds per annum, and the flow sheet design incorporates a Large Diamond Recovery capacity of up to 45mm.
Commercial production at the plant is expected to commence in the second quarter of 2017.
The company said that the concrete work is likely to end by this summer, after which structural steel will be erected in June.
Stornoway Diamond expects to complete the construction of the building by the fourth quarter of this year, followed by installation of the temperature sensitive crushing and recovery circuits during the first half of 2016.
The company said that 49% of the engineering work was completed last month.
It announced that DRA Americas and AMEC Americas have taken up the engineering and field support services relating to the plant and its diamond recovery circuits.
