Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Block caving
- Sub-level caving
|
Production Start | ...  |
Mine Life | 2031 |
Cullinan Mine is the world’s most important source of very rare blue diamonds.
At the Cullinan Mine Petra will establish a CC1 East sub-level cave, on the same level as the current C-Cut operation, extending the mine plan to 2031. The capital investment is estimated at US$173 million over the life of the project and is expected to deliver a project internal rate of return (IRR) of more than 30% and incremental project net present value (NPV) of more than US$70 million. Capital expenditure began during the Year and production is expected to begin in FY 2024, ramping up to a steady state in FY 2026. |
Source:
p. 171,189

Petra Diamonds Ltd.: 74%
Kago Diamonds (Pty) Ltd: 14%
Itumeleng Petra Diamonds Employee Trust (IPDET): 12%.
The IPDET holds a 12% interest in each of the Group’s South African operations, with Petra’s commercial BEE Partners holding the remaining 14% interest through their respective shareholdings in Kago Diamonds, in which Petra has a 31.46% interest. The effective interest percentages of Petra Diamonds attributable to Cullinan is 78.4%.
Contractors
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Summary:
The pipe intruded rocks of the Transvaal Supergroup as well as igneous rocks of the Bushveld Igneous Complex. The kimberlite has been radiometrically dated at 1179 ± 36 Ma using Rb–Sr in clinopyroxene and 1202 ± 72 Ma using U–Pb in perovskite. The pipe is itself intruded by a gabbro sill of 1150 Ma.
The internal geology of the pipe was first described by Wagner who noted the presence of a “floating reef” of Waterberg quartzite which occurred in the middle of the pipe and was associated with a considerable rubble zone of rounded quartzite and sandstone boulders. These Waterberg quartzite inclusions indicated the presence of this formation at the time of emplacement, but which has since been eroded from the area. Later geological work identified the presence of a number of discrete kimberlite varieties that included two major types of TKB, named the “Brown” and “Grey” kimberlites. The large floating reef referred to above occurred within the Grey Kimberlite along the boundary with the Brown. In addition, a central complex that consisted of several phases of kimberlite occurred within the Grey. This was referred to as the Black Kimberlite, which has an associated variety called the Piebald Kimberlite. The last phase of magmatism was the intrusion of carbonate-rich dykes.
Mining Methods
- Block caving
- Sub-level caving
Summary:
Mining method: Underground block cave and sub-level cave.
The sole source of our current tonnage is the C-Cut, a 5.7 Ha area with potential for approximately 34 Mt additional tonnage which is known to include high-value Type II stones, large high quality, white or blue gem-stones.
During the Year, the CC1-East project was approved and the capital spend has commenced. This new area is expected to begin to contribute from FY 2024 and to ramp up to steady state by FY 2026. It extends the mine plan to 2031. Whilst the C-Cut mining block is known for its Type II diamonds, the CC1E mining block has a higher grade than the C-Cut.
The significant opportunities for mine plan extensions beyond 2031 include additional tunnels to the east of the C-Cut, the C-Cut Centre block which has not been mined. The D-Cut and material below CC1-East depends on building a new shaft. This western part of the orebody at deeper levels should continue to produce high value stones.
Petra relies on tunnels to access and extract ore from draw-bells within underground block caves and thus face the inevitable threat of tunnel convergence. While tunnels are designed to withstand the significant structural stresses, geology is neither consistent nor entirely predictable and, where complex structures meet unfavourable geology, there is a possibility of tunnel convergence. Typically, the solution is to plug the affected area of the tunnel with concrete to strengthen it ........

Source:

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Flow Sheet:
Summary:

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Production:
The Company is not able to precisely measure the ROM/tailings grade split because ore from both sources is processed through the same plant; the Company therefore back-calculates the grade with reference to resource grades.
Commodity | Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Diamond
|
carats
| ......  | ......  | ......  | ......  | 1,368,720 | 786,509 | 680,813 |
All production numbers are expressed as mineral.
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Operational Metrics:
Metrics | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 |
Tonnes processed
| ......  | ......  | ......  | 5,075,441 t | 4,153,835 t | 2,389,087 t |
Annual processing capacity
| ......  | ......  | ......  | 6 Mt | | |
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Reserves at June 30, 2022:
Resource bottom cut-off: 1.0mm.
Reserve bottom cut-off: 1.0mm.
Category | Tonnage | Commodity | Grade | Contained carats |
Probable
|
34.5 Mt
|
Diamond
|
38.6 cpht
|
13.31 M carats
|
Indicated
|
219.6 Mt
|
Diamond
|
59.2 cpht
|
130.04 M carats
|
Inferred
|
169.5 Mt
|
Diamond
|
10.1 cpht
|
17.19 M carats
|
Total Resource
|
389.1 Mt
|
Diamond
|
37.8 cpht
|
147.23 M carats
|
Type | Material | Diameter | Length | Description |
Heavy Mobile Equipment as of May 7, 2022:
HME Type | Quantity |
Load-Haul-Dump (LHD)
|
.......................
|
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Corporate Filings & Presentations:
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