Targeting 360 000 carats per annum, production at Storm Mountain Diamonds’ Kao mine in Lesotho continues 24/7 with electric power generation provided via a Cat generator plant supplied and commissioned by Barloworld Power that provides a dedicated ‘off-the-grid’ solution.

Situated at around 2 500m above sea level, Storm Mountain Diamond’s Kao open pit mine is one of the world’s highest gemstone operations and in statistical terms has the largest undeveloped diamondiferous-bearing pipe in Lesotho. This is also the fourth largest such pipe in southern Africa from a coverage perspective at 19.8 hectares, with an indicated and inferred resource base of 12.7 million carats. Kao’s pipe has been explored and confirmed to 500m.

Unlocking the potential, the stakeholders in Storm Mountain Diamonds comprise London Stock Exchange listed entity, Namakwa Diamonds, with 62.5%, the Lesotho Government, owning 25%, with the balance allocated to private Lesotho investors.

A deposit with exceptional prospects, the site yields rare coloured diamonds ranging from purple, pink, yellow and top light brown to the classic ‘blue white’. Globally, ‘fancy coloured’, also known as rare diamonds, are regarded as an exceptional investment, with demand particularly strong in Asian markets. The pinks and the purples tend to be the rarest.

Key sizes at Kao are in the 3, 4 and 5 gemstone carat range, plus the real opportunity for major 100 carat and larger discoveries in a region well known for record finds.

Contextually, the mine site is surrounded by the sweeping vista of Lesotho’s snow-capped Maloti Mountain range in the country’s northern-most region, a remote location that is also the ancestral home of hardy Basutho settlements that depend mostly on subsistence farming in this high altitude climate. In fact some 600 villagers live within Storm Mountain Diamonds’ lease area, of which approximately 165 are employed by the mine.

Temperatures at this altitude tend to be cool all year round and particularly harsh in the winter months: the thermometer can easily plunge to minus 17ºC and below, placing heavy demands on man and machines

Then there’s the power factor. The Kao region is not connected to Lesotho’s national electrification grid, so from the onset Storm Mountain Diamonds needed to find an alternative, subsequently appointing Barloworld Power, Caterpillar’s southern African power systems dealer, to provide a turnkey generation solution.

Commissioned in early 2012, Barloworld Power’s scope of works entailed the design, installation and commissioning of a comprehensive 8 MVA prime and standby facility, including the synchonisation panel, transformers and MV switchgear (400 kVa stepping up to 11 V). This Barloworld Power installation ensures 24/7 continuous operation for the mine’s process plant and overall electrification requirements.

As Barloworld Power project manager, Rajesh Singh explains the installation comprises five Cat 3512B containerised generator units, de-rated from 1600 to 1350 kVA due to the altitude factor. To meet the mine’s power demand, the system is designed so that four generators are in continuous operation, and the fifth on standby.

“In addition to providing a contingency backup, having a reserve generator means that the mine can constantly rotate sets during routine servicing without concerns about downtime and ensuing power interruptions,” says Singh.

Alpine-themed V-shaped roofs and snow ducts provide all-weather protection, plus each generator has a diesel day tank equipped with inline heating. Storm Mountain Diamonds bulk tanks have a holding capacity of 755 000 litres, which caters for 10 days operation.


Providing some historical background, Storm Mountain Diamonds’ General Manager, Jan Venter, says that the company acquired the mine from its previous owners on 18th February 2010.

“During the prefeasibility stage we employed an existing 40 tonne an hour sampling plant to conduct intensive metallurgical test work. This period extended from May 2010 to June 2011 and the findings accurately determined our grades and our downstream revenues,” he explains.

Development at Kao is split into two phases. Phase 1, which has an envisaged three and a half year horizon, is in full ramp-up from January 2012. Mine infrastructure investments, amounting to around R380 million, include the recent completion of a 500 000m³ fresh water dam, built at the headwaters of the Kao River, the ongoing development of the slimes dam, plus the installation of the process plant facility.

Open pit mining entails the extraction and processing of hard rock kimberlite (referred to as K6) and weathered kimberlite material (named K-Other). Current production output is around 19 000 carats a month, split approximately 80 / 20 in terms of K6 and K-Other, yielding 18 carats and 7 carats per hundred tonnes, respectively.

Some 800 000 tonnes of K6 and 2.8 million tonnes of K-Other will be processed annually in Phase 1, together with 9 million tonnes of basalt waste, the latter subsequently being used for the ongoing construction of the mine’s slimes containment facility. Being steadily completed over the next 36 months, this facility will have a completed wall height of 60m, which has been determined by the mountainous typography.

“As we remove the waste we construct the wall,” says Venter, “the slimes dam having a final design capacity of 4.5 million cubes in line with our process plant output projections.” The process plant selected for Phase I is a 500 tonne per hour hybrid facility that optimally caters for both K6 and K-Other materials.

Meanwhile, Phase II, which has an anticipated life of mine of 15 years, offers major ‘blue sky’ potential, with plans to invest a further R1.5bn. “Upgrading the plant to 1000 tonnes per hour, we envisage mining 140 million tonnes of K-Other hard material over this period” Venter continues.

Moving these overall material volumes is the responsibility of load and haul contractor, Lephema Executive Transport (Lephema), which operates a dedicated Cat earthmoving fleet on site, supplied and supported by Barloworld Equipment.   Lephema’s units include 18 Cat 730 articulated trucks (ideally matched to mine the K6 keyhole development), with two Cat 345D hydraulic excavators performing the primary loading task.

“The commonality of Barloworld technical support on both the Cat earthmoving and generator units provides peace of mind, especially given our isolated location,” says Venter.

In the near future, Storm Mountain Diamonds intends to interface their Cat power station with the mine’s process plant SCADA system. This will enable real-time condition monitoring, as well as the capability to automatically start and stop the generators online.

“In the next two years or so, there’s the possibility of connecting to the Lesotho electrification grid. Either way, though, our Cat generators will always ensure that we can effectively manage our power demand without the risk of lost production,” he adds.


For further information, contact:
Jan Venter
General Manager
Storm Mountain Diamonds

For Barloworld Power media enquiries, contact:
Alastair Currie
Media Relations Manager
Barloworld Equipment
Tel: 011-929-0000