Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Gravity separation
- Counter current decantation (CCD)
- Concentrate leach
- Carbon in leach (CIL)
- Merrill–Crowe
- Cyanide (reagent)
|
Mine Life | 4 years (as of Jan 1, 2020) |
In addition to a planned mine life of 4 years, a prefeasibility study for the life-of-mine extension has been completed which considers a two- to three-year mine life extension and annual gold production of approximately 190 000oz. This study has now progressed to feasibility stage, with study work expected to be completed during FY21. |
Source:
p. 129
The mine is 100% owned and managed by Harmony through Morobe Consolidated Goldfields.
Deposit Type
- Vein / narrow vein
- Breccia pipe / Stockwork
Summary:
The deposit is a structurally controlled vein-stockwork gold-silver deposit located in the Morobe Granodiorite of the Wau Graben. Goldsilver mineralisation is contained in carbonate-adularia- quartz-sulphide vein-stockworks and in a few instances in hydrothermal breccias. Discrete zones of intense stockwork fracture and mineralised veining comprise individual lodes. At the Hidden Valley deposit, gold and silver are related to steeply to moderately dipping sheeted vein swarms associated with an underlying shallow thrust.
Summary:
Mining operations occur in two open pits 6km apart, Hidden ValleyKaveroi and Hamata of which Hidden Valley-Kaveroi is the largest. Both mines employ conventional open pit mining techniques with backhoe excavators and rigid dump trucks as the primary load and haul equipment. Front-end loaders are used for crusher feed and stockpile reclaim. A number of articulated smaller dump trucks are used for construction and to a lesser extent mining in Hamata.
Mining bench configuration generally consists of 18m inter-berm heights, blasted in 2m x 9m benches with 3m mining flitches.
Waste is disposed of in engineered valley fill waste dumps, with toes keyed in and buttressed using competent non-acid forming rock. Waste from the Hidden Valley-Kaveroi open pit is currently placed in the valley fill Western Sector and Niekywe waste dumps. A new dump, the Kaveroi Creek dump, will be built this year which, in combination with the current Western Sector dump, will provide full life of mine capacity for waste material, as well as capacity for potential extensions.
Crusher / Mill Type | Model | Size | Power | Quantity |
SAG mill
|
|
|
|
1
|
Summary:
A crushing facility is located near the Hidden Valley pit with the crushed ore conveyed via a 3.8km long overland pipe conveyor. Ore from the Hamata pit is trucked to the Hamata crushing station, located next to the ore processing plant.
Processing
- Gravity separation
- Counter current decantation (CCD)
- Concentrate leach
- Carbon in leach (CIL)
- Merrill–Crowe
- Cyanide (reagent)
Source:
Summary:
The Hidden Valley process plant was designed to treat nominally 4.1Mtpa of gold/silver bearing ore. The process uses a two stage crushing circuit followed by a SAG mill, gravity, CCD/Merrill Crowe circuit for silver and a carbon-in-leach circuit for the gold. A silver/gold ore bar is produced and flown off site for refining and sale.
Tailings are disposed of in a terrestrial tailings storage facility located to the south-west of the process plant. Dam-wall construction of the tailings storage facility is ongoing and largely constitutes placement of suitable oxide and fresh competent material sourced from mining in the Hamata pit and nearby quarry. The processing inventory in this ore reserve estimate is constrained by the remaining storage capacity. The Hidden Valley Extension study contemplates construction of an additional facility, TSF2.
Recoveries & Grades:
Commodity | Parameter | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Gold
|
Head Grade, g/t
| ......  | ......  | 1.36 | 1.07 | 1.51 | 1.84 |
Gold
|
Recovery Rate, %
| ......  | ......  | | | 86.5 | 86.6 |
Production:
Commodity | Units | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Gold
|
oz
| ...... ^ | ......  | ......  | 92,015 | 95,327 | 72,566 | 94,601 |
Silver
|
oz
| | | | | | ......  | ......  |
All production numbers are expressed as metal in doré.
^ Guidance / Forecast.
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Operational Metrics:
Metrics | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Tonnes milled
| ......  | 3,886 kt | 2,499 kt | 2,889 kt | 3,456 kt | 3,648 kt |
Annual processing capacity
| ......  | 4 Mt | 4 Mt | 4.2 Mt | 4.2 Mt | |
Total tonnes mined
| ......  | | | | 8,954 kt | 17,566 kt |
Ore tonnes mined
| ......  | | | | 3,062 kt | 4,554 kt |
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Reserves at June 30, 2020:
Hidden Valley 2020 cut-off 0.85 g/t.
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
2.3 Mt
|
Gold
|
1.32 g/t
|
98 koz
|
Proven
|
2.3 Mt
|
Silver
|
27.37 g/t
|
2,029 koz
|
Probable
|
14.5 Mt
|
Gold
|
1.61 g/t
|
749 koz
|
Probable
|
14.2 Mt
|
Silver
|
24.83 g/t
|
11,314 koz
|
Proven & Probable
|
16.8 Mt
|
Gold
|
1.57 g/t
|
847 koz
|
Proven & Probable
|
16.5 Mt
|
Silver
|
25.18 g/t
|
13,343 koz
|
Measured
|
2.3 Mt
|
Gold
|
1.32 g/t
|
93 koz
|
Measured
|
2.3 Mt
|
Silver
|
27.37 g/t
|
2,029 koz
|
Indicated
|
61.9 Mt
|
Gold
|
1.53 g/t
|
3,053 koz
|
Indicated
|
60 Mt
|
Silver
|
23.29 g/t
|
44,917 koz
|
Inferred
|
1.5 Mt
|
Gold
|
1.08 g/t
|
50 koz
|
Inferred
|
1.3 Mt
|
Silver
|
19.92 g/t
|
808 koz
|
Total Resource
|
65.7 Mt
|
Gold
|
1.52 g/t
|
3,201 koz
|
Total Resource
|
63.6 Mt
|
Silver
|
23.37 g/t
|
47,754 koz
|
Commodity Production Costs:
| Commodity | Units | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Cash costs
|
Gold
|
USD
|
|
|
824 / oz
|
1,252 / oz
|
1,320 / oz
|
1,230 / oz
|
Cash costs
|
Gold
|
USD
|
...... †
|
...... †
|
669 / oz†
|
1,068 / oz†
|
1,028 / oz†
|
1,065 / oz†
|
All-in sustaining costs (sold)
|
Gold
|
USD
|
|
|
1,261 / oz
|
1,417 / oz
|
1,564 / oz
|
1,557 / oz
|
All-in sustaining costs (sold)
|
Gold
|
USD
|
...... †
|
...... †
|
1,094 / oz†
|
1,241 / oz†
|
1,282 / oz†
|
1,395 / oz†
|
† Net of By-Product.
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Operating Costs:
| Units | 2017 | 2016 |
Total operating costs ($/t milled)
|
USD
| 33 | 39 |
Financials:
| Units | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Capital expenditures (planned)
|
M USD
| ......  | | | |
|
|
|
Capital expenditures
|
M USD
| | ......  | ......  | 122 |
98
|
10
|
62
|
Revenue
|
M USD
| | ......  | ......  | 32 |
110
|
216
|
272
|
Gross profit
|
M USD
| | ......  | ......  | 14 |
14
|
|
|
EBIT
|
M USD
| | | | |
|
-18
|
-28
|
EBITDA
|
M USD
| | | | |
|
6
|
26
|
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Aerial view:
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