OceanaGold : Exploration JORC Table 1 Report

Criteria

JORC Code explanation

Commentary

Sampling techniques

• Nature and quality of sampling (eg cut channels, random chips, or specific specialised industry standard measurement tools appropriate to the minerals under investigation, such as down hole gamma sondes, or handheld XRF instruments, etc). These examples should not be taken as limiting the broad meaning of sampling.

• Include reference to measures taken to ensure sample representivity and the appropriate calibration of any measurement tools or systems used.

• Aspects of the determination of mineralisation that are Material to the Public Report.

• Reverse Circulation (RC) drill hole samples comprise 95% of the drilling at Macraes. The remaining 5% are from sampled diamond core.

• The RC sampling, logging and assay protocol has been in place since 1994.

• Reverse circulation drill holes are sampled on 1 metre intervals from which 2 to 4kg sub-samples are riffle split.

• The 2 to 4kg was pulverised to produce a 50g charge and assayed for Au by fire assay at the SGS (NZ) Ltd Macraes site laboratory.

• A certified reference sample (CRM) is inserted every 20th sample

• Representative RC drill chips for each 1 metre are collected and placed in plastic chip trays which are stored onsite at the Macraes Gold Project (MGP) for future reference.

• Assay pulps are recovered from SGS (NZ) and stored onsite at MGP for future reference.

• Diamond drill core is photographed, logged, sawn to half core and sampled by OceanaGold personnel at the onsite core shed.

• Sample lengths are generally 1 metre lengths, or less, as dictated by lithological contacts.

• Fire assay for Au is undertaken at SGS (NZ) Ltd MGP site laboratory.

• A certified reference sample (CRM) is inserted every 20th sample.

• The remaining half cut core and assay pulps are stored onsite at MGP for future reference.

Drilling techniques

• Drill type (eg core, reverse circulation, open-hole hammer, rotary air blast, auger, Bangka, sonic, etc) and details (eg core diameter, triple or standard tube, depth of diamond

• The RC drill holes were obtained by using a reverse circulation drill rig with a 135mm face sampling hammer.

• The diamond drill core was obtained generally using triple tube HQ

Criteria

JORC Code explanation

Commentary

tails, face-sampling bit or other type, whether core is oriented and if so, by what method, etc).

diameter drilling, however, on occasions due to poor ground conditions was reduced to NQ.

Drill sample recovery

• Method of recording and assessing core and chip sample recoveries and results assessed.

• Measures taken to maximise sample recovery and ensure representative nature of the samples.

• Whether a relationship exists between sample recovery and grade and whether sample bias may have occurred due to preferential loss/gain of fine/coarse material.

• The reverse circulation drilling was sampled in 1 metre intervals. Sample recovery was estimated from visual inspection of sample bags with a target of > 90% recovery. For the drill holes reported sample recovery was considered acceptable. It is OceanaGold's procedure that if a reverse circulation drill hole goes wet, drilling is stopped and completed with a diamond tail. Reverse circulation drill hole sampling at MGP under wet conditions is prone to sampling grade bias.

• For diamond drilling recovery is recorded for every run and in general core recovery is in excess of 95%. Triple tube drilling was used to maximize core recovery through the Au mineralised zones.

• Analysis of grade versus core recovery does not show any relationship to be present.

Logging

• Whether core and chip samples have been geologically and geotechnically logged to a level of detail to support appropriate Mineral Resource estimation, mining studies and metallurgical studies.

• Whether logging is qualitative or quantitative in nature. Core (or costean, channel, etc) photography.

• The total length and percentage of the relevant intersections logged.

• RC drilling is logged every 1 metre using Macraes Gold Project logging codes that have been in place since 1994.

• Diamond core was geologically logged and photographed following OceanaGold's standard operating procedure for core logging. The geological logging process documents lithological and structural information as well as basic geotechnical information on RQD and major defects. Core logging generally identifies the upper surface of the mineralised shear. RC chip logging is not definitive about the position of this contact. Consequently geological interpretation uses a combination of logged geology and gold grade data.

• Drill holes were generally logged and sampled from 20m above the Hangingwall contact. If position of Hangingwall contact uncertain holes were logged and sampled in their entirety.

Sub- sampling techniques and sample preparation

• If core, whether cut or sawn and whether quarter, half or all core taken.

• If non-core, whether riffled, tube sampled, rotary split, etc and whether sampled wet or dry.

• For all sample types, the nature, quality and appropriateness of the sample preparation technique.

• Quality control procedures adopted for all sub-sampling stages to maximise representivity of samples.

• Measures taken to ensure that the sampling is

• RC 1 metre samples are collected into a cyclone and then split through a riffle or cone splitter. Close attention is paid to ensure each interval sampled is 1 metre. Drilling advance is paused at the end of each 1 metre, to allow the entire sample to clear the splitter prior to resuming drilling. The cyclone and splitter are kept clean.

• Half core was cut along the inferred long axis of the mineralised ellipse to achieve a representative sample.

• Sub-sampling size is considered appropriate and the method representative for the style and thickness of mineralisation. This is

Criteria

JORC Code explanation

Commentary

representative of the in situ material collected, including for instance results for field duplicate/second-half sampling.

• Whether sample sizes are appropriate to the grain size of the material being sampled.

borne out by 26 years of mining at Macraes.

• Where sufficient core is available, generally >15kgs and preferably

• Metallurgical sampling aims to be as geologically and spatially representative as possible.

• RC chips cannot be used at MGP for metallurgical sampling due to contamination with hammer oil which negatively impacts sulphide float test work.

>30kgs of quarter cut core, metallurgical samples are selected. Due to the volume requirement this means a metallurgical sample may consist of material from multiple holes.

Quality of assay data and laboratory tests

• The nature, quality and appropriateness of the assaying and laboratory procedures used and whether the technique is considered partial or total.

• For geophysical tools, spectrometres, handheld XRF instruments, etc, the parametres used in determining the analysis including instrument make and model, reading times, calibrations factors applied and their derivation, etc.

• Nature of quality control procedures adopted (eg standards, blanks, duplicates, external laboratory checks) and whether acceptable levels of accuracy (ie lack of bias) and precision have been established.

• At MGP, SGS (NZ) Ltd operates an assay laboratory under contract to OceanaGold (NZ) Ltd.

• QAQC procedures involve the use of certified reference material, lab duplicates, and lab standards. Sample batches are re-assayed if 1 of the OceanaGold CRM's is outside defined limits.

• Samples checked off against submission sheet.

• Samples are then dried at 150 degrees until visibly dry.

• Entire sample is crushed. Crush size is under 5mm and approximately 500g is retained for pulverising.

• The 500 gram sample is pulverised to 90% passing 75 micron.

Sample preparation RC

Sample preparation diamond

1. Samples checked off against submission sheet.

2. Samples are then dried at 150 degrees until visibly dry.

3. Entire core pre-crushed using a crusher. Nominal top size is 30mm (in one dimension only).

1. Entire sample is crushed. Crush size is under 5mm and approximately 500g is retained for pulverising.

2. The 500 gram sample is pulverised to 90% passing 75 micron.

Assay

50g fires assays were completed using SGS's FAA505 scheme.

1. 50 gram of sample is weighed with 170 gram of lead flux and tumble mixed in a plastic pot.

Criteria JORC Code explanation Commentary

2. contents are transferred to a crucible and fusion of the gold in the sample with the lead in the flux occurs in a LPG fired blast furnace at 1,100 degrees C.

1. cupellation of the lead button to recover the gold prill then occurs in an LPG fired muffle furnace set at 950 degrees C.

2. the prills are recovered from the cupels, digested in plastic test tubes with aqua regia. Gold determinations by atomic absorption.

Q/QC is checked and results released.

Verification of sampling and assaying

• The verification of significant intersections by either independent or alternative company personnel.

• The use of twinned holes.

• Documentation of primary data, data entry procedures, data verification, data storage (physical and electronic) protocols.

• Discuss any adjustment to assay data.

• Geological logging is compiled digitally using Tough Books at the drill site or the core shed.

• At hole completion the digital log is loaded into the MGP acQuire exploration database and validated.

• Geological observation of mineralisation is generally well correlated with assay results.

• No adjustments are made to the assay data received from SGS (NZ) Ltd.

Location of data points

• Accuracy and quality of surveys used to locate drill holes (collar and down-hole surveys), trenches, mine workings and other locations used in Mineral Resource estimation.

• Specification of the grid system used.

• Quality and adequacy of topographic control.

• All drill hole collars are surveyed by OceanaGold mine surveyors using MGP grid to an accuracy of +/- 0.10 metre

• All drill holes are down hole surveyed every 30m using a digital down hole camera.

• Topographic control is by detailed aerial surveys of mine and prospect areas to 0.5m accuracy.

Data spacing and distribution

• Data spacing for reporting of Exploration Results.

• Whether the data spacing and distribution is sufficient to establish the degree of geological and grade continuity appropriate for the Mineral Resource and Ore Reserve estimation procedure(s) and classifications applied.

• Whether sample compositing has been applied.

• Drill hole spacing at the exploration stage is initially at 100m by 100m spacing. If drill holes intersect significant mineralisation the drill hole spacing is progressively reduced to limited infill to 25 x 25 metres. RC drill holes are sampled in 1 metre intervals. Diamond drill holes are generally sampled in 1 metre intervals unless hole geology dictates otherwise.

• Average spacing of Hangingwall pierce points for FRUG is 50 by 50 metre grid spacing.

Orientation of data in relation to geological structure

• Whether the orientation of sampling achieves unbiased sampling of possible structures and the extent to which this is known, considering the deposit type.

• If the relationship between the drilling orientation and the orientation of key mineralised structures is considered to

• Surface drill holes are generally vertical to intersect a generally 15 to 25 degree dipping gold mineralised structure.

• Whilst this direction is sub-optimal for steeply dipping quartz vein arrays, near-vertical reverse circulation and diamond drilling has been used as the basis for resource definition MGP since 1985.