DiamondCorp has started development tunnelling on the doming level at the Lace mine, 200km south-west of Johannesburg, South Africa, after completing back-filling activities.
According to the company, tunnelling on the 290m level is progressing in high-grade K4 kimberlite.
Prior to this, steel arched sets have been installed for a 10m section through the centre of the slot drive cross cut on the level.
The kimberlite contains less internal waste compared with the lower-grade K6 kimberlite on the southern side of the pipe due to tunnel advances being achieved at the originally planned rate, the company said.
Development tunnels are required to pass through the pipe before entering the high-grade Upper K4 (UK4) mining block, which is expected to start in December.
Workers and machinery at the Lace mine need to access the level in order to begin drilling and blasting of the slot between the 290m and 310m production levels.
The slot will provide the initial ramp-up in mining tonnages from the UK4 block.
DiamondCorp CEO Paul Loudon said: "Resumption of development work on the 290m level combined with commissioning last week of the 400t per hour conveyor belt system from the first production level, means that many of the operational challenges we have been facing in recent months have been overcome, albeit that the overall development and production timetable remains behind schedule, as previously announced.
"I am very pleased that these challenges have been met without any injuries to our workforce or damage to our equipment."
Recently, the company commissioned a 400t/h underground conveyor belt system at the Lace mine.