Star Diamond Mine

The Star Diamond Mine is located 2km NE of the town of Theunissen in the Free State Province of South Africa. It forms part of a prominent east-west fissure system that stretches approximately 15km. The property comprises a single mining licence (ML 11/1996) of 246.29 hectares.

The Mine has been in operation for more than 60 years and all necessary mine infrastructure exists. The mine is serviced by both bitumen and non-bitumen roads. A 99KV Eskom power line services the mine and in addition a managed substation is on the property. A private grass airstrip exists on the mine property.

The Star Diamond Mine is operated by Star Diamonds (Pty) Ltd under old order mining licence no ML 11/1996 and converted to a new order mining licence in terms of item 792) of Schedule II of the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDa0 and issued by the Department of Minerals and Energy (DMR) on the 16 April 2009, for a period of 15 years ending 10 February 2025.

Petra Diamonds Southern Africa (Pty) Ltd acquired the Star Diamonds Mine in 2005 from Crown Diamonds NL. Sedi Diamonds, a South African subsidiary of Frontier acquired the Star Diamonds Mine from Petra though the acquisition of Star Diamonds (Pty) Ltd in 2014. Sedi Diamonds appointed Frontier Mining Projects (Pty) Ltd as the man contractor to operate its diamond operations in South Africa.

The Star Diamond Mine was established in 1948 and has operated continuously since that date exploiting a series of kimberlitic fissures over an east-west trending strike length of 4.5km. 

The Star Diamond Mine is currently operating at depths of between 580 and 620 metres below the surface.  The individual fissures range in width from 5 to 80 centimetres, with an average width of 58cm.The five fissure units from west to east are the Clewer, Micaceaous, Burns, east Star and Wynandsfontein fissures.  The kimerlites have been intruded into quartzites and sandstones of the Witwaatersand Supergorup, overlain by a 520m thiskc sequence of flat lying shales and sandstones of the Karoo Supergroup, with the Karoo rocks being intruded by a thick dolerite sill.

The Star Diamond Mine extends over a 4.5km section of the east-west trending Star fissure system, which can be traced for a length of some 15km. Star consists of a number of en-echelon fissures, with these being separated by up to 150m in a north-south direction, with up to 40m jogs within individual fissure units. The five fissure units, from west to east, include Clewer, Micaceaous, Burns, East Star and Wynandsfontein as indicated in the geological model of the resource below,

There had previously been issues with methane collecting at the contact between the Karoo and Witwaatersand at the western end of the Star Mine which had preclyded development belwo the 12/13 leval at that end of the mine. This has now been controlled, however mining will not take place at levels 12 & 13 at the western end.

The Company’s strategy is to significantly increase operational efficiencies and reduce operating costs at the Star Mine. Currently ore at the Star Mine is hand mucked, which is labour and time intensive. It is planned to change this to a water jetting method, which will reduce the cost and time to recover material and increase product assurance on diamond handling of large stones. Through the water jetting process the Company believes that it is possible to increase the recovered grade from 40 cpht to 55 cpht.

The current key bottleneck at the Star Mine is hoisting, with only a single 1.3t cocopan being able to be hoisted at a time. The Company is currently installing a skip in the shaft and a skip loader at level 16 (the main haulage level), with surface bins then to be converted to accept material from the skips which will then be connected to the plant by conveyor. Concurrently an incline shaft is being dug from level 16 to level 19 for haulage purposes with the shaft being deepened to level 17.

To facilitate operations at the western end of the Star Mine (with methane now actively managed) a 1.5m diameter raise bore is being installed from level 14 to be used as a return airway.