Modern Mining: Featured News

ASX-listed Frontier Diamonds has reported the recovery of the first diamonds from its Bellsbank kimberlite pipe exploration project in the Northern Cape. The diamonds were recovered from a plant commissioning sample taken from the pipe, with the biggest stone being 1,45 carats.

Bellsbank Sedibeng Plant

The bulk sample and tailings retreatment plant at Sedibeng.

Discussing the results, Frontier’s CEO, Jan Louw, said the quality of diamonds recovered from the sample was very encouraging and supported Frontier’s decision to proceed to the next phase in developing the asset.

“We will now focus our efforts on increasing the pit layout to enable us to access the primary kimberlite pipe and conduct an adequate bulk sample. The newly commissioned plant facilities give us the added advantage of performing the bulk sample programme at a relatively low overall cost and in an expedited manner. We are proceeding with an economic assessment of the Bellsbank pipe and are looking forward to reporting the next round of results once finalised.”

The Bellsbank property is located 10 km west of Frontier’s Sedibeng diamond mine, located approximately 110 km north-west of Kimberley. The pipe is a 130 m x 80 m ‘blow’ on a proven fissure system and was discovered through ground magnetics and gravity surveying.

A geological report regarding the Bellsbank kimberlite pit is being prepared by the Com­petent Person (CP) and will include a review of historic and current exploration results.

According to Frontier, the recovery of the first diamonds from the processing of a plant commissioning sample taken from the upper levels of the calcretised kimberlite facies of the Bellsbank pipe is a positive indication of the mineralisation of the asset, while the gem qualities appear similar to the existing Sedibeng production. Lower uncalcretised kimberlite is expected to be intersected at a depth of 27 m as established by historic drilling records.

No definitive diamond grade (cpht) has been determined given the limited volumetric material processed. According to the CP, the current commissioning sample can be regarded as sub-economic ‘mineralised waste’. It appears to be low-grade in-situ mineralisation that cannot be classified as either a mineral resource or ore reserve and is intended for stockpiling.

The Bellsbank sample material was processed via the newly commissioned bulk sample processing plant facility located at Sedibeng. The plant consists of a scrubber, primary crusher, secondary crusher circuit, plus coarse and fines pan with concentrate being processed on a batch basis through the current Sedibeng DMS and X-ray plant.

The facility has a designed nameplate capacity of 50 t/h for kimberlite ore and 150 t/h for tailings feed. It has been designed to operate in a dual capacity as both a batch treatment plant for bulk samples extracted from Bellsbank, as well as other regional exploration targets, and as a concentrate retreatment plant to process available tailings material from the Sedibeng mine. There are currently more than 2 Mt of diamond-bearing tailings material sitting at the mine.

The plant was purchased for US$0,6 million from a local dump retreatment operator, Superkolong, a subsidiary of Batla Minerals SA. Relocation and refurbishment of the plant began in July 2017, using exclusively the in-house engineering expertise at Frontier’s contracted associate company’s Kimberley workshop. It was successfully refurbished and wet commissioned at a total engineering cost of approximately US$0,6 million. Frontier says the total capital investment of approximately US$1,2 million can be measured against an estimated replacement value of the plant of approximately US$4,7 million.

The entire crushing and screening process of the sample at the new Sedibeng plant, together with the treatment of the screened product at the existing DMS plant, and subsequent sorting of the diamonds, was overseen by the CP over a period of five days. Two days were used to thoroughly clean and purge the DMS and final recovery plants before processing the sample.

Frontier will proceed to commission a public geological report accompanied by historic and current exploration results, including a description of the style and nature of mineralisation. This report will consider the results of the next 10 m blast, which will expose the underlying hypabyssal kimberlite. Grade estimations will be established after taking a sufficient bulk sample of the exposed kimberlite.

Apart from the Northern Cape properties, Frontier – which debuted on the ASX in January this year – also controls the Star diamond mine, which is located 12 km north-east of the town of Theunissen in Free State Province. Both Star and Sedibeng are well-established underground mines with more than 60-year operating histories. They were acquired by Sedi Diamonds (now a subsidiary of Frontier) in 2014 from Petra. Frontier’s MD is Jan Louw, previously Director of Operations of Firestone Diamonds.

Photos courtesy of Frontier Diamonds.

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