JOHANNESBURG (miningweekly.com) – Dual-listed DiamondCorp has marked another milestone as it develops its 74%-owned Lace diamond mine, in the Free State.

The last week of March saw the diamond mining, development and exploration company kick off the first sale of kimberlite diamonds from the mine since 1931 through a combination of direct sales and competitive tenders, with all lots on offer sold.

In December, the mine marked the start of the ramp-up process towards commercial production from underground for the first time since October 1930, with full production of 30 000 t/m expected by July.

The company said in a statement on Tuesday that it experienced “good demand” in all size categories, with 8 648 ct of the diamonds recovered during bulk testing sold.

Around 6 247 ct of kimberlite diamonds greater than 1.25 mm in diameter fetched some $1.09-million, at an average of $175/ct, while 2 401 ct of tailings diamonds and fine diamonds less than 1.25 mm in diameter were sold for $46 000, representing an average of $19/ct.

“We are extremely pleased with the level of demand shown for the Lace production and the prices we achieved in all size categories. Overall sentiment in the diamond market remains relatively positive compared to the end of 2015, and the price increases seen in January are being maintained,” DiamondCorp CEO Paul Loudon said.

Included in the sale was a 22.11 ct diamond that had been sold into DiamondCorp's beneficiation joint venture as an H-coloured stone at $5 000/ct and a 1.08 ct Type II purple stone, which sold at tender for $6 363/ct.

“The 22.11 ct stone has been cut and polished into two stones – a 7.19 ct F-coloured VVS2 emerald shape diamond and a E/F-coloured 0.85 ct pear shape diamond. The company will receive an additional 50% of the profit from these stones when the polished diamonds are sold,” he explained.

Meanwhile, underground mining and development at Lace resumed in January and remained on target for production of 30 000 t/m by July, while tailings retreatment resumed as an adjunct to the processing of kimberlite from underground.

During the three months to March 31, the mine recovered 3 438 ct of diamonds.

This comprised 6 324 t of K4 kimberlite at an average recovered grade of 36 carats per hundred tonnes (cpht), 8 327 t of K6 kimberlite from ventilation tunnel development at average recovered grade of 8 cpht and 18 307 t of tailings at an average recovered grade of 5 cpht.