Database
integrity
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·
Measures taken
to ensure that data has not been corrupted by, for example,
transcription or keying errors, between its initial collection and
its use for Mineral Resource estimation purposes.
·
Data validation
procedures used.
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· The
Newmont drilling data was supplied by TMPL as an MSAccess database
which had been compiled by the previous holders of the property,
AusTinMining. This data was re-imported into an MSAccess database
to allow for some error checking.
· The
TMPL recent drilling data was supplied as a series of CSV files
which H&SC imported into the same MSAccess database as used for
the Newmont drilling.
· TMPL
digital logging process involves android
based Lenovo Tab M10 HD tablets. The tablet has a rugged plastic
and rubber waterproof case and requires a pin code to unlock. The
tablet has various templates stored on it for recording different
data sets (RC logging, DDH logging, RQD's etc). All templates are
MSExcel spreadsheets and operate via manually typing in the data on
the tablet or utilizing pre-filled drop-down boxes.
· Validation of the Newmont drilling by H&SC included
original assay and logging sheet checks against the supplied
digital data for a set of 13 randomly selected drillholes. Minor
typographic errors were noted and fixed. Some of the methodology of
transcribing the hard copy data could be improved.
· H&SC completed some independent validation of the new data
to ensure the drill hole database is internally consistent.
Validation included checking that no assays or geological logs
occur beyond the end of hole and that all drilled intervals have
been geologically logged. The minimum and maximum values of assays
and density measurements were checked to ensure values are within
expected ranges. Further checks include testing for duplicate
samples and overlapping sampling or logging intervals.
· H&SC takes responsibility for the accuracy and reliability
of the data used in the Mineral Resource estimates.
· H&SC used the historic local N-S orthogonal grid for all
interpretation and modelling work. For subsequent mine planning
studies this work was rotated and converted to MGA94 Zone 56 using
the Surpac 2 point grid transformation option.
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Site visits
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·
Comment on any
site visits undertaken by the Competent Person and the outcome of
those visits.
·
If no site
visits have been undertaken indicate why this is the
case.
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· Two
site visits were completed by Simon Tear of H&SC, in October
2022 during the recent drilling campaign and again in June 2023 to
review newly drilled diamond core and other aspects of the sample
data collection phase.
· The
October 2022 visit involved inspection of both ongoing diamond and
RC drilling operations. A check on collar coordinates for 20 holes
including both historic and recent holes was completed. A review of
chip trays for 2 RC drillholes was also undertaken. Inspection of
the trial adit and its recent TMPL sampling was also
completed.
· The
June 2023 visit involved inspection of 6 DD holes from the recent
hole twinning programme designed by TMPL to test previous results
from the Newmont drilling. The inspection confirmed the geology,
mineralisation and assay grades at Taronga as comprising thin,
cassiterite-bearing veins, in a sheeted vein system, hosted within
hornfels rock.
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Geological
interpretation
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·
Confidence in
(or conversely, the uncertainty of ) the geological interpretation
of the mineral deposit.
·
Nature of the
data used and of any assumptions made.
·
The effect, if
any, of alternative interpretations on Mineral Resource
estimation.
·
The use of
geology in guiding and controlling Mineral Resource
estimation.
·
The factors
affecting continuity both of grade and geology.
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· The
mineralisation comprises North Pit and South Pit zones with a
relatively lower grade zone in between (partly the result of a lack
of drilling and a change in the host lithology with possibly a
change in the rheological properties of the host).
· The
North Pit comprises two higher grade elongate tin zones with an
enveloping zone of lower grade tin forming a single mass. Whilst
the South Pit comprises up to five distinct and well separated
elongate tin-enriched zones with parallel strike and
dip.
· The
host rock is the result of relatively uniform hornfelsing of either
siltstone or sandstone.
· Mineralisation consists of quartz-cassiterite veins from
hairline fractures to veins up to 5-10cm thick. Chalcopyrite and
arsenopyrite disseminations, blebs and veinlets are commonly
associated with the tin-bearing veins. Minor pyrite zones are
occasionally visible.
· There
is no obvious visible lithological or structural control to the tin
mineralisation, save for a broad NE/SW striking enriched zone,
presumably some form of structural corridor. The system has been
interpreted as a sheeted vein deposit.
· No
geological interpretation per se has been completed as the tin
grades define the tin mineralization in the rather
amorphous-looking hornfels. Any wireframe for the tin
mineralization would ultimately be a simple grade shell.
· There
is insufficient data to define with confidence any specific or
significant fault structure.
· A
review of multi-element data from the recent drilling has allowed
for the interpretation of a sodium depletion zone corresponding
with a weak potassic enrichment as matching the definition of the
tin mineralisation. The study also highlighted a lithogeochemical
difference between the host rocks for the South and North
Pits.
· An
oxidation surface, reflecting both complete and partial weathering,
was developed by H&SC from logged historic and recent drilling
data, with support from the multielement assays. Confidence in the
surface is moderate as the data is incomplete and there is
uncertainty as to whether weathering has formed a broad, horizontal
front roughly parallel to the surface topography and/or that there
are more isolated, penetrative fingers of weathering to greater
depths via fault structures.
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Dimensions
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·
The extent and
variability of the Mineral Resource expressed as length (along
strike or otherwise), plan width, and depth below surface to the
upper and lower limits of the Mineral Resource.
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· The
Mineral Resources have a strike length of around 2.7km in a north
easterly (grid north) direction. The plan width of the resource
varies from 200m to 400m with an average of around 270m. The upper
limit of the mineralisation is exposed with the fresh rock
generally occurring around 20m below surface and the lower limit of
the Mineral Resources extends to an approximate depth of 550m below
surface (400mRL).
· The
lower limit to the Mineral Resource is a direct function of the
depth limitations to the drilling in conjunction with the search
parameters. The mineralisation is open at depth and laterally to
the southwest, beyond the South Pit zone.
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Estimation and modelling
techniques
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·
The nature and
appropriateness of the estimation technique(s) applied and key
assumptions, including treatment of extreme grade values,
domaining, interpolation parameters and maximum distance of
extrapolation from data points. If a computer assisted estimation
method was chosen include a description of computer software and
parameters used.
·
The availability
of check estimates, previous estimates and/or mine production
records and whether the Mineral Resource estimate takes appropriate
account of such data.
·
The assumptions
made regarding recovery of by-products.
·
Estimation of
deleterious elements or other non-grade variables of economic
significance (eg sulphur for acid mine drainage
characterisation).
·
In the case of
block model interpolation, the block size in relation to the
average sample spacing and the search employed.
·
Any assumptions
behind modelling of selective mining units.
·
Any assumptions
about correlation between variables.
·
Description of
how the geological interpretation was used to control the resource
estimates.
·
Discussion of
basis for using or not using grade cutting or
capping.
·
The process of
validation, the checking process used, the comparison of model data
to drill hole data, and use of reconciliation data if
available.
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· The
drillhole database was composited with no constraints to 1m
composites covering the whole of the prospect.
· Ordinary Kriging (OK) with two search domains was used to
complete the tin grade estimation using H&SC's in-house GS3M
modelling software. The geological interpretation and block model
creation and validation was completed using the Surpac mining
software. H&SC considers OK to be an appropriate estimation
technique for the type of mineralisation and extent of data
available. The tin composite data has a relatively low coefficient
of variation of approximately 1.6 (CV = standard deviation divided
by the mean).
· Regression equations based on newly available assay data were
used to estimate missing copper, arsenic and sulphur composite
values. The arsenic and sulphur datasets are a lot smaller in
number compared to the copper and silver data. Correlation between
the various elements was modest to weak but generated regression
equations based on the tin grade, using the Conditional Expectation
technique, resulted in plausible outcomes for Cu, As, Ag & S.
It should be noted that the copper, arsenic, silver and sulphur are
not reported as part of the Mineral Resources and that the numbers
are generated from less data than that used in the tin Mineral
Resources; the elements were modelled to allow for waste rock
characterisation. OK was also used to model these other
elements.
· A
total of 35,176 1m composites, excluding residuals (137), were
generated from the drillhole database and modelled for tin, copper,
arsenic, silver & sulphur.
· Grade
interpolation was unconstrained, except by the search parameters
and the variography, in acknowledgement of the gradational nature
to the margins of the tin mineralisation and the abundance of
peripheral assays.
· There
were very minor zones of unsampled core which were generally
surrounded by very low grades and therefore did not require the
insertion of very low grades. These areas were invariably allocated
very low block grades from the subsequent grade
interpolation.
· The
base of oxidation was treated as a soft boundary. No cover surface
was created as the mineralisation is outcropping and is exposed in
many places along its ridge line and flanks.
· No
top-cutting was applied as extreme values were considered by
H&SC as not significant and therefore top-cutting was
considered unnecessary.
· An OK
check model using the same composite data was completed using the
OK option in Surpac. The outcome confirmed the original model. A
check Multiple Indicator Kriging model (in the GS3M software) was
completed using the same composite data. Again the outcome
confirmed the original model. An OK check model without the JACRO
composite data yielded very similar outcomes to the original
Measured and Indicated Resources.
· Block
dimensions are 5m by 10m by 5m (Local E, N, RL respectively) with
no sub-blocking. The north dimension was chosen as it is around
half to a third of the nominal drillhole distances in the detailed
drilled area of the South Pit. The east dimension was chosen to
take into account the geometry and thickness of the mineralisation
in the South Pit. The vertical dimension was chosen to reflect the
sample spacing and possible mining bench heights and to allow for
flexibility in potential mining scenarios.
· Two
search domains were employed, one for the South Pit (domain 1) and
another for the North Pit (domain 2) respectively, reflecting a
modest change in strike between the two zones.
· All
elements were modelled as a combined dataset. 5 search passes were
employed with progressively larger radii or decreasing data point
criteria. The Pass 1 used radii of 35m by 35m by 5m (along strike,
down dip and across mineralisation respectively), Passes 2, 3 and 4
used 50m by 50m by 10m, 70m by 70m by 10m & 100m by 100m by 20m
respectively, Minimum number of data was 12, maximum number of data
was 32 with a minimum of 4 octants. A fifth pass used 100m by 100m
by 20m with a minimum of 6 data points from at least 2
octants.
· The
maximum extrapolation for the Mineral Resources was in the order of
100m down dip and 100m along strike to the NE.
· The
resource estimates are controlled by the data point distribution,
the variography, block size and the search ellipse. Conventional
use of wireframes to control the mineralisation was not considered
necessary. A preliminary resource model had been completed prior to
the 2022/3 drilling to ascertain likely dilution grades for
peripheral material to the main tin mineralisation with the
subsequent infill drilling results generally matching this
preliminary model.
· The
new block model was reviewed visually by H&SC and it was
concluded that the block model fairly represents the grades
observed in the drill holes. H&SC also validated the block
model using a variety of summary statistics and statistical plots.
No issues were noted.
· Comparison with the 2013 resource estimates indicated a larger
tonnage for the 2023 Mineral Resource at approximately the same tin
grade. The main increase in tonnage was for the South Pit due to
the modelling method extrapolating much further than the rather
tight wireframes that were used previously to constrain the
mineralisation. The increase is also mainly the result of the
additional exploratory TMPL drilling to the south west. Also
greater confidence in the Newmont drilling data has been achieved
with the twin holes and the repeat adit sampling to allow for
Measured Resource to be categorised.
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Moisture
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·
Whether the
tonnages are estimated on a dry basis or with natural moisture, and
the method of determination of the moisture
content.
|
· Tonnages of the Mineral Resources are estimated on a dry
weight basis.
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Cut-off
parameters
|
·
The basis of the
adopted cut-off grade(s) or quality parameters
applied.
|
· The
resources are reported at a tin cut-off of 0.05% based on the
outcome of a recently completed throughput study by independent
mining consultants AMDAD of Brisbane.
· The
cut-off grade at which the resource is quoted reflects the intended
bulk-mining approach.
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Mining factors or
assumptions
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·
Assumptions made
regarding possible mining methods, minimum mining dimensions and
internal (or, if applicable, external) mining dilution. It is
always necessary as part of the process of determining reasonable
prospects for eventual economic extraction to consider potential
mining methods, but the assumptions made regarding mining methods
and parameters when estimating Mineral Resources may not always be
rigorous. Where this is the case, this should be reported with an
explanation of the basis of the mining assumptions
made.
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· The
Mineral Resources were estimated on the assumption that the
material is to be mined by open pit using a bulk mining
method.
· The
proposed mining method is a conventional drill & blast, truck
& excavator with extracted material sent to an on-site ROM pad
with a processing plant adjacent to the planned pit.
· Minimum mining dimensions are envisioned to be around 10m by
5m by 5m (strike, across strike, vertical respectively). The block
size is relatively larger than the likely minimum mining
dimensions.
· The
resource estimation includes internal mining dilution.
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Metallurgical factors or
assumptions
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·
The basis for
assumptions or predictions regarding metallurgical amenability. It
is always necessary as part of the process of determining
reasonable prospects for eventual economic extraction to consider
potential metallurgical methods, but the assumptions regarding
metallurgical treatment processes and parameters made when
reporting Mineral Resources may not always be rigorous. Where this
is the case, this should be reported with an explanation of the
basis of the metallurgical assumptions made.
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· Industry standard processing is envisaged for the
deposit.
·
A processing flowsheet has been proposed that will
involve comminution, gravity separation and floatation to generate
a tin concentrate.
· The
hardness of ore material is at a manageable level.
· Initial testwork has demonstrated that penalty elements can be
limited to acceptable levels.
·
Waste products from processing can suitably be
dealt with.
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Environmen-tal factors or
assumptions
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·
Assumptions made
regarding possible waste and process residue disposal options. It
is always necessary as part of the process of determining
reasonable prospects for eventual economic extraction to consider
the potential environmental impacts of the mining and processing
operation. While at this stage the determination of potential
environmental impacts, particularly for a greenfields project, may
not always be well advanced, the status of early consideration of
these potential environmental impacts should be reported. Where
these aspects have not been considered this should be reported with
an explanation of the environmental assumptions
made.
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· The
deposit lies within hilly, open country typical of the NSW Northern
Tablelands.
· Land
use is predominantly cattle grazing on native or improved
pasture.
· There
are limited flat areas for waste and tailings disposal. Most likely
sites are north of a ridge line just north of the proposed
pits.
· Thera
are a small number of creeks with seasonal flows.
· The
host rocks have relatively low sulphur contents.
· Some
of the mined material has acid neutralising capacity.
· Baseline data collection of a variety of environmental
parameters is in progress e.g. biodiversity, surface water and
groundwater.
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Bulk
density
|
·
Whether assumed
or determined. If assumed, the basis for the assumptions. If
determined, the method used, whether wet or dry, the frequency of
the measurements, the nature, size and representativeness of the
samples.
·
The bulk density
for bulk material must have been measured by methods that
adequately account for void spaces (vugs, porosity, etc), moisture
and differences between rock and alteration zones within the
deposit.
·
Discuss
assumptions for bulk density estimates used in the evaluation
process of the different materials.
|
·
Original bulk density measuring work completed by
Newmont used single pieces of core subjected to the weight in
air/weight in water method (Archimedes Principle). The result was a
set of default densities: 2.8t/m3 for 'ore' (>0.1%Sn)
and 2.7t/m3 for waste.
·
The 2013 Mining One estimate used a global default
of 2.75t/m3.
·
Work completed by TMPL used a weight in air/weight
in water procedure on 415 samples of diamond core. The average
value was 2.75t/m3.
·
Core inspection indicated very competent core with
no significant vughs.
·
H&SC subdivided the samples using the base of
oxidation surface to ascertain the impact of surface weathering on
the density. The impact was marginal with slightly lower values in
the oxidized zone as would be expected. Default values were
inserted into the block model for oxide and fresh rock that had
interpolated grades for the North Pit, and the Hillside and Payback
subdivisions of the South Pit.
·
A density of 2.65t/m3 was applied to
all 'waste' i.e. blocks with no interpolated tin grade.
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Classification
|
·
The basis for
the classification of the Mineral Resources into varying confidence
categories.
·
Whether
appropriate account has been taken of all relevant factors (ie
relative confidence in tonnage/grade estimations, reliability of
input data, confidence in continuity of geology and metal values,
quality, quantity and distribution of the data).
·
Whether the
result appropriately reflects the Competent Person's view of the
deposit.
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· The
classification of the resource estimates is based on the data point
distribution which is a function of the drillhole
spacing.
· A
defined shape was used for the Measured Resource in the North Pit
in order to remove a 'spotted dog' effect.
· Other
aspects have been considered in the classification including, the
style of mineralisation, the geological model, validation of the
historic drilling, sampling methods and recoveries, non-sampled
zones, the QAQC programme and results and comparison with previous
resource estimates.
· H&SC believes the confidence in tonnage and grade
estimates, the continuity of geology and grade, and the
distribution of the data reflect Measured, Indicated and Inferred
categorisation. The estimates appropriately reflect the Competent
Person's view of the deposit. H&SC has assessed the reliability
of the input data and takes responsibility for the accuracy and
reliability of the data used to estimate the Mineral
Resources.
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Audits or
reviews
|
·
The results of
any audits or reviews of Mineral Resource
estimates.
|
· No
audits or reviews have been completed.
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Discussion of relative
accuracy/ confidence
|
·
Where
appropriate a statement of the relative accuracy and confidence
level in the Mineral Resource estimate using an approach or
procedure deemed appropriate by the Competent Person. For example,
the application of statistical or geostatistical procedures to
quantify the relative accuracy of the resource within stated
confidence limits, or, if such an approach is not deemed
appropriate, a qualitative discussion of the factors that could
affect the relative accuracy and confidence of the
estimate.
·
The statement
should specify whether it relates to global or local estimates,
and, if local, state the relevant tonnages, which should be
relevant to technical and economic evaluation. Documentation should
include assumptions made and the procedures used.
·
These statements
of relative accuracy and confidence of the estimate should be
compared with production data, where available.
|
· No
statistical or geostatistical procedures were used to quantify the
relative accuracy of the resource. The global Mineral Resource
estimates of the Taronga deposit are moderately sensitive to higher
cut-off grades but does not vary significantly at lower
cut-offs.
· The
relative accuracy and confidence level in the Mineral Resource
estimates are considered to be in line with the generally accepted
accuracy and confidence of the nominated Mineral Resource
categories. This has been determined on a qualitative, rather than
quantitative, basis, and is based on the Competent Person's
experience with similar deposits and geology.
· The
Mineral Resource estimates are considered to be accurate globally,
but there is some uncertainty in the local estimates due to the
current drillhole spacing, a lack of geological definition in
certain places eg fault zones and penetration depths of surface
weathering,
· No
mining of the deposit has taken place, so no production data is
available for comparison.
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