Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Crush & Screen plant
- Jig plant
- Dense media separation
- X-Ray sorting
- Grease belt/table recovery
|
Mine Life | 50 years (as of Jan 1, 2021) |
16 November 2021 - The mine was placed on care and maintenance in April 2020 in order to preserve its liquidity, at a time when diamond pricing was impacted by the COVID-19 pandemic, and operations recommenced in Q1 FY 2022. |
Latest News | Petra Diamonds executes Williamson Diamonds MoU December 20, 2021 |
Source:
p. 22
Company | Interest | Ownership |
Government of Tanzania
|
25 %
|
Indirect
|
Petra Diamonds Ltd.
|
75 %
|
Indirect
|
Williamson Diamonds Ltd.
(operator)
|
75 %
|
Direct
|
Williamson Diamonds Limited ("WDL") is the operator of the Williamson diamond mine in Tanzania that is owned 75% by PDL (Petra Diamonds Ltd.) and 25% by the Government of Tanzania.
On 13th December 2021 Petra Diamonds announced a new Framework Agreement in principle with the Government of Tanzania which will result in Petra’s share in the Williamson Diamond Mine becoming 63%, with the Government holding the remaining 37% share. This Framework Agreement will require Petra shareholder approval – the Circular for which will be published on the website once it has received approval from the UK’s Financial Conduct Authority.
Summary:
The mine is an open pit operation based upon the 146 hectare Mwadui kimberlite pipe, which is the world’s largest economic kimberlite to have seen continuous mining.
Despite having been in operation since 1940, the pit is only 95 metres at its deepest point due to the large size of the deposit. The low grade of the deposit is countered by the high value of its diamonds and lends itself well to high volume, bulk mining methods.
Summary:
The mine is an open pit operation based upon the 146 hectare Mwadui kimberlite pipe, which is one of the world’s largest economic kimberlites.
Despite having been in operation since 1940, the pit is only 105 metres at its deepest point due to the large size of the deposit. The low grade of the deposit is countered by the high value of its diamonds and lends itself well to high volume, bulk mining methods.
Processing
- Crush & Screen plant
- Jig plant
- Dense media separation
- X-Ray sorting
- Grease belt/table recovery
Source:
Summary:
Once a diamond operation yields ore, the diamonds must be sorted from the other materials. Excavated ore is transported to a processing plant.
The kimberlite is first crushed and then processed through the plant, which consists of a series of screens, jigs and scrubbers and a gravity pan or DMS plant to remove lighter particles and create a concentrate of heavy material, which includes the diamonds.
Diamonds are then extracted from this material by using an X-ray machine and/or grease table and checked by hand sorting. Most diamonds luminesce under X-rays and can therefore be identified and separated in final recovery. However, some diamonds – particularly more valuable Type II stones – do not respond well to X-rays, so grease tables are used to recover such stones. As diamonds are hydrophobic (meaning they repel water), they stick to the grease while the rest of the wet concentrate runs off.
The treatment of ROM kimberlite ore produces a sink (high den ........

Recoveries & Grades:
Commodity | Parameter | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Diamond
|
Head Grade, carats/t
| ......  | ......  | 0.07 | 0.06 | 0.05 | 0.05 |
Production:
FY 2022 Guidance - assuming production restart in H1 FY 2022.
Commodity | Units | 2022 | 2020 | 2019 | 2018 | 2017 | 2016 |
Diamond
|
carats
| ...... ^ | ......  | ......  | 341,102 | 225,202 | 212,869 |
^ Guidance / Forecast.
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Operational Metrics:
Metrics | 2022 | 2020 | 2019 | 2018 | 2017 |
Ore tonnes mined
| ......  | | | | |
Tonnes processed
| ......  | ......  | 5,495,470 t | 5,045,284 t | 4,071,592 t |
^ Guidance / Forecast.
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Reserves at June 30, 2021:
Resource bottom cut-off: 1.15mm.
Reserve bottom cut-off: 1.15mm.
Category | Tonnage | Commodity | Grade | Contained carats |
Probable
|
48.6 Mt
|
Diamond
|
0.069 carats/t
|
3.36 M carats
|
Indicated
|
63.4 Mt
|
Diamond
|
0.049 carats/t
|
3.08 M carats
|
Inferred
|
958 Mt
|
Diamond
|
0.036 carats/t
|
34.77 M carats
|
Total Resource
|
1,021 Mt
|
Diamond
|
0.037 carats/t
|
37.86 M carats
|
Operating Costs:
| Units | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Total operating costs ($/t milled)
|
USD
| 10.2 | 11.1 | 10.7 | 11.6 | 11 | 12 |
Financials:
| Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Capital expenditures (planned)
|
M USD
| ......  | | | | |
|
|
Capital expenditures
|
M USD
| | ......  | ......  | ......  | 4.6 |
15
|
24.4
|
Revenue
|
M USD
| | ......  | ......  | ......  | 68.5 |
58.4
|
78.9
|
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Corporate Filings & Presentations:
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News:
Aerial view:
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