Oceanagold Haile Optimisation Study Delivers Enhanced Value

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MEDIA RELEASE

26 June 2017

OCEANAGOLD HAILE OPTIMISATION STUDY DELIVERS ENHANCED VALUE

(All financial figures in US Dollars unless otherwise stated)

(MELBOURNE) OceanaGold Corporation (TSX/ASX: OGC) (the “Company”) is pleased to announce the

completion of the Haile Optimisation Study (“Optimisation Study” or “Study”) where results demonstrate

enhanced value through upgraded mineral reserves, increased annual gold production, longer mine life and

robust economics.

Key Highlights

 Increased Proven and Probable gold reserves by over 70% from 2.02 Moz to 3.46 Moz

 Announced a maiden reserve on the Horseshoe deposit of 0.44 Moz.

 Revised mine plan that includes larger open pit operations for a 16-year mine life and an underground

operation at Horseshoe for a 6-year mine life.

 Planned expansion of the process plant from 3 Mtpa to 4 Mtpa to support higher mining rates and

increased annual production.

 Robust economics with undiscounted pre -tax cash flows of $1.4 billion based on current reserves

plus an additional $400 million of undiscounted cash flows inclusive of total current resources .

 Further extensional and standalone exploration potential to increase value and mine life.

Mick Wilkes, OceanaGold President and CEO said, “ The solid economics of the Haile Optimisation Study

clearly demonstrate what we have long believed to be the inherent value of this top -tier asset in South

Carolina. Mineral reserves have now increased over 70% from original estimates , supporting increased

annual production while increasing mine life to at least 16 years. The maiden reserve at the Horseshoe

deposit of 0.44 Moz and a larger open pit operation within our existing land package is a positive outcome.”

“We expect significant cash flow generation from Haile where the Study has determined $1.4 billion in

undiscounted pre -tax cash flows on current reserves only and $1 .8 billion including total current mining

inventory.”

He added, “Very shortly, we will commence the permitting process and work closely with the regulator and

all stakeholders to advance the Haile expansion project to construction. In the meantime, we cont inue to

ramp up operations and drill targets at depth and along strike to further add to the already significant resource

base. These targets include Palomino and beneath the Snake pit both of which were not included in the study

and represent potential additional value of the asset.”

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Revised Mineral Resources & Reserves

Proven and Probable Reserves have increased over 70% from previous estimates to 3.4 6 Moz of gold.

Following a successful resource definition drill program on the upper portion of the Horseshoe deposit in

2016, the Company is pleased to announce a maiden Reserve 0.44 Moz for the Horseshoe underground,

which also has a total Inferred Resource of 0.20 Moz.

The Company has revised the mine plan and design of the surface operations. Pit optimisations were run on

a $1,300/oz gold price assumption with an $1,150/oz gold price shell selected for pit design ( previously

$950/oz gold price). This has resulted in larger pits with the total open pit reserves now standing at 3.02 Moz

of gold.

Table 1 – Updated Haile Reserves

Table 2 – Haile Measured & Indicated Resources

Table 3 – Haile Inferred Resource

Reserves are reported within mine designs based on US$1,300/oz gold price assumption

Estimates of contained metal do not make allowances for processing losses

Resources are reported inclusive of reserves

Mineral resources that are not ore reserves do not have demonstrated economic viability

The open pit resource is reported within a US$1,500/oz optimised shell

The underground resource cut-off grade is based on US$1,500/oz gold price

All figures are rounded to reflect the relative accuracy of the estimates

Revised Haile Mine Plan

With the larger open pits and inclusion of an underground operation at Horseshoe, the Company has revised

the overall mine plan. Following completion of construction of an underground operation and expansion of

the process plant, ore feed will be sourced at a rate of 3.3 million tonnes per year from surface operations

and 0.7 million tonnes per year from underground. The open pit operations currently have a mine life of 16

years while the Horseshoe underground has a mine life of 6 years.

PROJECT

AREA Cut-off Mt Au g/t Au Moz Mt Au g/t Au Moz Mt Au g/t Au Moz

HAILE Open Pit 0.45g/t Au 7.55 1.97 0.48 47.5 1.66 2.54 55.0 1.71 3.02

HAILE Underground 1.50g/t Au 3.12 4.38 0.44 3.12 4.38 0.44

TOTAL 7.55 1.97 0.48 50.6 1.83 2.98 58.2 1.85 3.46

PROVEN PROBABLE PROVEN & PROBABLE

PROJECT

AREA Cut-off Mt Au g/t Au Moz Mt Au g/t Au Moz Mt Au g/t Au Moz

HAILE Open Pit 0.45g/t Au 7.06 1.97 0.45 52.2 1.63 2.73 59.2 1.67 3.17

HAILE Underground 1.17g/t Au 2.71 5.68 0.49 2.71 5.68 0.49

TOTAL 7.06 1.97 0.45 54.9 1.83 3.22 61.9 1.84 3.67

MEASURED INDICATED MEASURED & INDICATED

PROJECT

AREA Cut-off Mt Au g/t Au Moz

HAILE Open Pit 0.45g/t Au 11 1.4 0.49

HAILE Underground 1.17g/t Au 1.2 5.0 0.20

TOTAL 12 1.7 0.69

INFERRED

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The larger open pits necessitate the need for additional tailings and waste capacity including the addition of

a new PAG cell, however the revised design is within the Company’s existing land package.

Figure 1 – Revised Open Pit and Underground Layout

Table 4 – Mining Physicals (based on Reserves only)

Mine Production Value Units

Open Pit

Ore 55.0 Mt

Waste 481.2 Mt

Strip Ratio 8.7 : 1 waste:ore

Average Gold Grade 1.71 g/t

Contained Gold 3,018 koz

Underground

Ore 3.1 Mt

Average Gold Grade 4.38 g/t

Contained Gold 439 koz

Combined

Total Ore 58.2 Mt

Total Waste 481.2 Mt

The Horseshoe deposit will be accessed from a portal originating from the north wall of the Snake open pit,

where the Company recently commenced mining ore, four months ahead of schedule. The mining method

for Horseshoe will be long -hole open stoping at a rate of 0.7 Mtpa from a single access and backfilled with

cemented rock fill. Mining costs are estimated to range between $35 and $40 per tonne mined. The Company

expects first ore from the underground in 2021 with pre-production development capital costs estimated to

be $55 million (excluding pre-production operating cost).

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Once underground, the Company will develop exploration drives to further drill the Horseshoe deposit at

depth and carry out additional and more comprehensive fan drilling of nearby underground target Palomino

and mineralisation beneath the Snake pit.

Figure 2 – Horseshoe Underground Design

Process Plant

The Study has identified an opportunity to expand the process plant from 3 Mtpa to 4 Mtpa to support the

higher overall mining rate. With the Company ramping-up and fine tuning the process plant over the course

of 2017, the Study has used a conservative approach to estimate the additional plant required to achieve the

higher throughput rate. The Company does expect to identify opportunities to reduce its upgraded plant to

achieve the higher throughout rates which would then in turn reduce capital costs. The current estimated

capital cost to upgrade the process plant is $67 million.

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Figure 3 – Process Plant Ore Feed (‘000 tonnes)

Figure 4 – Gold Production and Grade Profile

Haile Optimisation Study Economics

The results of the Study have demonstrated robust economics with undiscounted pre-tax cash flows of $1.4

billion based on current reserves only plus an additional $400 million inclusive of total current mining

inventory.

The capital cost associated with the pre-production development of the Horseshoe underground is estimated

to be $5 5 million, while the initial capital cost associated with a larger open pit and associated mining

infrastructure is expected to be $1 32 million, which includes $60 million allocated for upgrading the mining

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fleet. The expansion of the process plant to 4 Mtpa is estimated to be $67 million with potential costs savings

identified as the plant is currently ramping up . Overall sustaining capital cost is expected to be $245 million

over the 16-year mine life.

Operating costs for surface operations are expected to reduce to between $1.45 to $1.55 per tonne mined

while underground mining costs at Horseshoe are expected to range between $35 and $40 per tonne milled.

Processing costs are expected to remain unchanged at $10 to $11 per tonne milled.

Table 5 – Capital Costs

Description Initial Capital

$M

LOM Sustaining Capital

$M

Total

SM

Open Pit 67 75 142

Underground 55 26 81

Process Plant 67 25 92

Site Infrastructure 65 119 184

Total 254 245 499

Over the course of the coming months, the Company will release an updated National Instrument (“NI”) 43 -

101 Technical Report in relation to the updated mine plan and design at Haile. Furthermore, the Company

will prepare the permitting application for the larger open pit, underground mine, associated infrastructure

and expanded process plant. The Company expects the start of underground development in 2019 with first

underground ore processed in 2021.

- ENDS -

For further information please contact:

Investor Relations

Sam Pazuki

Tel: +1 416 915 3123

Jeffrey Sansom

Tel: +61 3 9656 5300

[email protected] | www.oceanagold.com | Twitter: @OceanaGold

About OceanaGold

OceanaGold Corporation is a mid -tier, high-margin, multinational gold producer with assets located in the

Philippines, New Zealand and the United States. The Company’s assets encompass its flagship operation,

the Didipio Gold-Copper Mine located on the island of Lu zon in the Philippines. On the North Island of New

Zealand, the Company operates the high-grade Waihi Gold Mine while on the South Island of New Zealand,

the Company operates the largest gold mine in the country at the Macraes Goldfield which is made up of a

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series of open pit mines and the Frasers underground mine. In the United States, the Company is currently

commissioning the Haile Gold Mine, a top -tier asset located in South Carolina. OceanaGold also has a

significant pipeline of organic growth and exploration opportunities in the Americas and Asia-Pacific regions.

OceanaGold has operated sustainably over the past 2 7 years with a proven track -record for environmental

management and community and social engagement. The Company has a strong social license to operate

and works collaboratively with its valued stakeholders to identify and invest in social programs that are

designed to build capacity and not dependency.

In 2017, the Company expects to produce 550,000 to 6 00,000 ounces of gold and 18,000 to 19,000 tonnes

of copper with sector leading All-In Sustaining Costs that range from $600 to $650 per ounce sold.

Technical Disclosure

The updates of Proven and Probable Reserves above have been verified by, are based on and fairly

represent information compiled by or prepared by Mr. J.G. Moore and Mr B. van Brunt. Messrs. Moorer and

van Brunt are a full -time employees of Oceana Gold (New Zealand) Limited and Haile Gold Mine, Inc

respectively. Mr Moore is a Member and Chartered Professional with the Australasian Institute of Mining and

Metallurgy. Mr van Brunt is a Fellow of the Australasian Institute of Mining and Metallurgy. All such persons

are “qualified persons” for the purposes of NI 43 -101 and have sufficient experience relevant to the style of

mineralisation and type of deposit under consideration and to the activity which they are undertaking to qualify

as a “competent person” as defined in the JORC Code.

Messrs Moore and van Brunt consent to inclusion in this public release of the matters based on their

information in the form and context in which it appears.

Cautionary Statement for Public Release

Certain information contained in this public release may be deemed “forward -looking” within the meaning of

applicable securities laws. Forward -looking statements and information relate to future performance and

reflect the Company’s expectations regarding the generation of free cash flow, execution of business

strategy, future growth, future production, estimated costs, results of operations, business prospects and

opportunities of OceanaGold Corporation and its related subsidiaries. Any statements that express or involve

discussions with respect to predictions, expectations, beliefs, plans, projections, objectives, assumptions or

future events or performance (often, but not always, using words or phrases such as "expects" or "does not

expect", "is expected", "anticipates" or "does not anticipate", "plans", "estimates" or "intends", or stating that

certain actions, events or results "may", "could", "would", "might" or "will" be taken, occur or be achieved) are

not statements of historical fact and may be forward -looking statements. Forward -looking statements are

subject to a variety of risks and uncertainties which could cause actual events or results to differ materially

from those expressed in the forward-looking statements and information. They include, among others, the

accuracy of mineral reserve and resource estimates and related assumptions, inherent operating risks ,

sovereign risks, risk of suspension and those risk factors identified in the C ompany’s most recent Annual

Information Form prepared and filed with securities regulators which is available on SEDAR at

www.sedar.com under the Company’s name. There are no assurances the Company can fulfi l forward -

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looking statements and information. Such forward -looking statements and information are only predictions

based on current information available to management as of the date that such predictions are made; actual

events or results may differ materially as a result of risks facing the Company, some of which are beyond the

Company's control. Although the Company believes that any forward -looking statements and information

contained in this press release is based on reasonable assumptions, readers ca nnot be assured that actual

outcomes or results will be consistent with such statements. Accordingly, readers should not place undue

reliance on forward-looking statements and information. The Company expressly disclaims any intention or

obligation to upda te or revise any forward -looking statements and information, whether as a result of new

information, events or otherwise, except as required by applicable securities laws. The information contained

in this release is not investment or financial product advice.

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