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Section 1 Sampling Techniques and Data
(Criteria in this section apply to all succeeding
sections.)
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Criteria
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JORC Code explanation
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Commentary
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Sampling
techniques
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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.
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Include
reference to measures taken to ensure sample representivity and the
appropriate calibration of any measurement tools or systems
used.
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Aspects of the
determination of mineralisation that are Material to the Public
Report.
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In cases where
'industry standard' work has been done this would be relatively
simple (eg 'reverse circulation drilling was used to obtain 1 m
samples from which 3 kg was pulverised to produce a 30 g charge for
fire assay'). In other cases more explanation may be required, such
as where there is coarse gold that has inherent sampling problems.
Unusual commodities or mineralisation types (eg submarine nodules)
may warrant disclosure of detailed information.
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While the bulk of the data is from exploration
work completed in the 1970s and 1980s by state-owned Wismut
company, Saxore completed since 2013 a confirmation channel
sampling, a bulk sampling program in Hämmerlein and a confirmation
drilling program at Dreiberg.
Historic Sampling:
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The historic sampling is based on diamond core
drilling, and channel sampling where the underground exploration
drifts did cut mineralisation and drilling was not
possible.
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Sampling was done based on standardized operating
procedures following the standards at that time.
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Channel sampling was done using an angle grinder
to cut two 2cm deep cuts 10 cm apart with the material between the
two cuts removed with a compressed air jackhammer.
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Drill core was logged and marked up for sampling
under geological control with 1 m being the dominant sample
interval and thereafter, core was split into halves using a core
splitter. One half was stored for further geological,
mineralogical, and processing investigations and the other half was
used for further sample preparation and analysis.
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The half-core sample was crushed in 2 steps. In
the first step, the sample was crushed with a double-toggle jaw
crusher to 100 % passing 10 mm. A single-toggle jaw crusher was
then used to crush the entire sample to below 1 mm. After
homogenization, the sample was divided until a representative 400 g
subsample was achieved. This sample was milled to a powder in the
last stage by using a vibratory disc mill. The resulting 400 g
sample had to fulfil the requirement of 95 % <65
μm. This was tested
internally as well as by external controls. From this final 400 g
sample, all sub-samples for different analysis.
Confirmation Sampling
(Saxore):
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From 2013 onwards, Saxore collected and assayed a
variety of samples as part of the project development. In 2015,
Saxore executed a targeted sampling programme comprising 66 channel
samples from accessible areas in Hämmerlein. A total of approx. 2.2
t of material was taken. Samples were subjected to a variety of
bench-scale tests including sorting, dense media separation,
magnetic separation, flotation, and gravity.
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The channels were cut using an electric rock saw
and jackhammer and were mainly cut V-shaped approximately 10-15 cm
wide and max. 11 cm deep. The material was
then chiselled out using the jackhammer.
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Diamond drilling was used to obtain 1 m samples,
depending on the lithology of HQ core which was sawn in half
longitudinally. The half core was bagged and sent to ALS Global for
assaying. This is industry standard
work.
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No samples from Reverse Circulation (RC) drilling
were used
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All core samples intersected the main Dreiberg
skarn were sent for assay after being logged by the
geologist.
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All drilling samples of the main skarn and
intervals approximately 10 to 20m above and below the skarn were
analysed.
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Drilling techniques
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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 tails, face-sampling bit or other
type, whether core is oriented and if so, by what method,
etc).
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Historic Drilling:
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Four main phases of drilling have been undertaken
from 1966 to 1991 from surface and underground
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All drill-core was 56mm in diameter (between NQ
and HQ) but for areas of difficult ground bigger core sizes were
used. There is no indication of how much difficult ground was
encountered. The 1970-75 drilling used an SBU SIF-650 surface rig
(rated to 1000m) and a SIF-300 and SIF-650 underground rigs.
Downhole geophysics was completed for the surface holes and most of
the underground holes but no digital data is available. The
1976-1981 underground drilling campaign used a GP-1 and BSK-2m-100
drilling rigs.
Confirmation Drilling:
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The primary aims were to confirm historic grades
and upgrade parts of the inferred resource to the next higher
category in accordance with the JORC Code (2012) by expanding the
data base in the thick skarn seams. Between 20 August 2022 and 23
April 2023, surface drilling was carried out. The project was
coordinated by Saxore and the drilling work was carried out by
GEOPS Bohrgesellschaft mbH and later by Pruy KG, Gesteins-, Bohr-
und Umwelt-Technik.
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Diamond drilling was undertaken by the contractor
GEOPS Bohrgesellschaft mbH. All drilling used PQ or HQ bits.
Directional drilling was done in NQ which was redrilled in
HQ. Drill rods were stabilized and triple tubing was used to
ensure good core recovery and avoid washing out of
cassiterite.
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Drilling was at an angle of -69° to-79° and hence
cuts across the skarn seams that are sub-horizontal.
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GEOPS Bohrgesellschaft mbH used drilling rigs from
Atlas Copco Crealius. The drilling by Pruy KG was carried out with
a HD 110 coring drilling rig mounted on a crawler. A total of 8
drill holes with a total length of 4365.7 m were drilled from 3
drill sites (including three test holes from Pruy from collar
SaxDRE036).
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The holes drilled by GEOPS Bohrgesellschaft mbH in
the period from 20 August 2022 to 30 December 2022 were cored.
Drilling without coring was performed at the top, where a standpipe
was drilled and in sections where directional drilling was carried
out to reach the target (downhole motor). Drill holes started with
PQ diameter and changed to HQ at a certain depth. NQ for
pre-drilling was necessary for directional drilling in some
parts.
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Drilling by Pruy KG in the period from 15 April
2023 to 22 April 2023 was carried out using a RC method, whereby
the rock is crushed at the bottom of the hole and transported to
the surface by compressed air in an inner tube and thus preventing
contamination. Systematic sampling did not
take place.
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All drilling, depth control and recovery was
supervised by project geologists
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Drill sample recovery
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Method of
recording and assessing core and chip sample recoveries and results
assessed.
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Measures taken
to maximise sample recovery and ensure representative nature of the
samples.
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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.
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Historic Drilling:
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Recovery data was supplied as a decimal fraction
of the measured length which HSC converted to a percentage. The
data contained recoveries for both channel sampling and diamond
drilling. HSC reviewed recoveries for the three mineral zones only,
primarily to establish if there was any bias with either the
sampling methods or with the tin grades. In all instances average
recovery was greater than 97% with 98.5%, 97.6% and 97.3 % for
Hämmerlein, Dreiberg and Zweibach respectively. No bias with either
the sampling method or the tin grade was observed.
Confirmation Drilling:
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All core intervals are measured and compared with
driller's marks to determine actual recovery. Recovery was
generally above 95% apart from isolated intervals with poor ground
conditions, generally either near surface or in fault zones. During
directional drilling no core or cuttings could be sampled.
The loss for these areas was 100%.
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No systematic core loss in mineralised zones was
noted.
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During coring, core recovery in fresh rock was
generally above 95 %, with the exception of disturbed or brecciated
areas. During directional drilling no core or cuttings could be
sampled. The loss for these areas was 100 %. It was agreed with the
drill contractor that directional drilling would no longer be used
100 metres above the target depth. No
systematic core loss was detected.
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Logging
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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.
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Whether logging
is qualitative or quantitative in nature.
Core (or
costean, channel, etc) photography.
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The total length
and percentage of the relevant intersections
logged.
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Historic
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Logging consisted of hand-written detailed
hardcopy log sheets completed by Wismut that have been transcribed
into digital data by Beak Consultants (based in Freiberg, Germany).
This included using numeric codes for the different lithotypes
(Appendix 2). The quality of the logging is good and includes the
added bonus of graphic logs.
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The main items have all been captured in the
digital database including the drill intervals, lithology, recovery
and assay data.
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The captured data has been compared with original
drill logs by Saxore for much of the database, as part of a manual
resource estimation. Only minor errors were noted and no
significant problems were found in the data checked.
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Validation of the drillhole database by HSC
included reviewing of 50 randomly selected hardcopy drillogs for
the three areas and comparing numbers etc for downhole surveys,
geological logging and assays. No
significant issues were noted.
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No core remains available for viewing. All core
was destroyed with the cessation of the uranium mining.
Confirmation:
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All diamond drill cores have been geologically
logged and photographed (wet and dry) to a level of detail to
support appropriate mineral estimation, mining, and metallurgical
studies.
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A logging of RC cuttings was omitted as no
mineralisation was expected in the near surface area of the planned
RC hole.
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Sub-sampling techniques and
sample preparation
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If core, whether
cut or sawn and whether quarter, half or all core
taken.
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If non-core,
whether riffled, tube sampled, rotary split, etc and whether
sampled wet or dry.
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For all sample
types, the nature, quality and appropriateness of the sample
preparation technique.
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Quality control
procedures adopted for all sub-sampling stages to maximise
representivity of samples.
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Measures taken
to ensure that the sampling is representative of the in situ
material collected, including for instance results for field
duplicate/second-half sampling.
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Whether sample
sizes are appropriate to the grain size of the material being
sampled.
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Historic:
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Assaying of Sn was carried out using the device
"MAK-1" (until 1974) and "Romul-EFA" (from 1974). Assays of MAK and
EFA were performed on site using a 5 g split of the sample
collected as described above.
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The MAK-1 device ('Mössbauer-Analysator für
Kassiterit': Mössbauer analyzer for cassiterite, which is a
Gamma-ray fluorescence analyzer) only determines the content of
oxidic Sn, as this device does not detect Sn in silicate minerals
and others (e.g., stanine). These values were recorded in the
database in the column "Sn_pc_MAK".
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The "Romul-EFA" device ('Element Fluoreszenz
Analyzer', which is an X-ray fluorescence analyzer) measures the
total Sn content with its two-channel elemental phase analyzer,
regardless of its mineralogy. These values were recorded in the
database in the column "Sn_pc_EFA".
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MAK and EFA was carried out on a 5 g chip sample
at the mine site in the laboratory in Pöhla. This was followed by
spectral analysis (AES) of all samples for the elements Zn, Pb, Cu,
In, Cd, As, W, Ag, As and Bi, whereby the prioritization of the
elements to be analyzed varied and changed over time. Elements such
as B, Ni, Co, but also F, P, Mn, Zr, V, Cr, Sr, Ge, Nb, Ta, Sb, Se,
Ga, Au, Y, La and Ce were also analyzed spectroscopically over time
and ranges. If the upper detection limit was overrated, X-ray
fluorescence analyses were performed for the elements Zn, Pb, Cu,
As, W, Bi and Cd. If the upper detection limit for the elements Cu
and In was exceeded, further atomic absorption spectrometric
analyses (AAS) was carried out.
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Iron and zinc were analyzed using FAAS, with total
iron reported as Fe2O3. DMT notes that total
iron includes Fe hosted by all Fe-bearing minerals reported in the
skarn mineralogy including magnetite, amphiboles, garnets, chlorite
and Fe-rich sphalerite, etc.
Confirmation:
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The drill core samples were sent to certified ALS
Laboratory in Rosia Montana, Romania.
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At the ALS laboratory in Rosia Montana, the sample
of core is crushed and split to around 1kg to finer than 2 mm using
method CRU-31, then pulverized in a mill to 85% finer than 75µm
using method PUL-32.
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Analysis of the diamond drill samples consisted of
a four-acid digest and ICP-AES for 33 elements. The samples were
also assayed for Sn and In using a lithium borate fusion and ICP-MS
technique. If over detection limits on the ICP was reached, then
the samples were assayed using XRF.
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Quality of assay data and laboratory tests
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The nature,
quality and appropriateness of the assaying and laboratory
procedures used and whether the technique is considered partial or
total.
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For geophysical
tools, spectrometers, handheld XRF instruments, etc, the parameters
used in determining the analysis including instrument make and
model, reading times, calibrations factors applied and their
derivation, etc.
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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.
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Historic:
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The devices of EFA and MAK were tested under
certain circumstances on samples of the Tellerhäuser deposit and
fulfilled the requirements considering accuracy, sensibility,
stability, reliability, and speed. The technique appears to be very
accurate up to 10% Sn but this is the maximum value it can usefully
detect, with anything over 10% Sn being reported as simply >10%
Sn.
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In order to control EFA and MAK an additional 5 g
split of the original 400 g pulverised sample was collected at
regular intervals (approximately 1 in 10) and sent to an external
laboratory, Grüna (Central laboratory of SDAG Wismut) where it was
analysed by a wet chemical method. The working routine was started
with an alkali fusion with Na2O2/NaOH fluxing
reagent (sample/reagent = 1/10). Leaching was undertaken with
distilled water and neutralized with HCl. Three grams of aluminium
were added to this solution to create reducing conditions. Small
grains of calcite were added to ensure the production of CO2 and
thus prevent the influence from oxygen in the air. This tin
solution then underwent a titration process with iodine utilizing
the reaction Sn2+ + I2 → Sn4+ + 2 I. By adding small drops of 0.1
molar iodine solution to the dissolved sample, an abrupt colour
change from transparent to blue appears at a certain level of added
iodine. Each 1 ml of added reagent corresponds to 0.5935 mg Sn in
the sample. By using the simple rule of proportion, the tin grade
of the original sample was thus calculated. These values were
recorded in the database in the column "Sn_pc_Chemie".
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An additional 5 g split of the original 400 g
sample was collected at regular intervals and sent to a third
laboratory as a check for the three techniques described above.
This was undertaken in the laboratory of the Ehrenfriedersdorf tin
mine and used the same assay technique as the Grüna Laboratory
(Central laboratory of SDAG Wismut), as described above.
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Assaying was checked by internal and external
control analyses. The measuring devices in the laboratories were
calibrated daily. Calibration was performed as standard on the
basis of various defined content classes.
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Within the sample batches, a minimum of 1 standard
per 20 samples was prescribed, but the rule was 1 in 10. These
standards were made from different materials of different content
classes and had different qualities in order to check the accuracy.
The standard measurements were recorded in the laboratory and kept
in the archive. Only the sample results were communicated to the
client (SDAG Wismut laboratory order).
Confirmation:
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Tin is a difficult element to analyse as
cassiterite is not soluble in acid. Thus, a sub-sample of the
pulverized and mixed material is taken and fused with lithium
borate. The fused bead is then analysed by a mass
spectrometer using method ME-MS85 which reports Sn and In. This
returns a total tin content, including tin as cassiterite.
Over limit assays of tin are re-analysed using method ME-XRF15b
which involves fusion with lithium metaborate with a lithium
tetraborate flux containing 20% NaNO3 with an XRF
finish.
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Other elements are analysed by method
ME-ICP61. This involves a 4 acid (HF-HNO3-HCLO4 digest, HCl
leach and ICP-AES finish). This is an industry standard
technique for Cu, Pb, Zn and Ag. A suite of 33 elements is
reported, including tin, which is only acid soluble tin in this
case and thus can be subtracted from the fusion tin assays to
obtain tin as cassiterite. The acid soluble tin is generally
associated within the lattice of silicates and Fe-oxides. It
is in some part significant as it has a main impact on tin
recovery.
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Prior to dispatch of samples, the following QA/QC
samples are added:
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Certified standards representative of the grades
expected are added at the rate of 1 in 20 samples.
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Blanks are added at the rate of 1 in 20
samples.
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Verification of sampling and assaying
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The verification
of significant intersections by either independent or alternative
company personnel.
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The use of
twinned holes.
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Documentation of
primary data, data entry procedures, data verification, data
storage (physical and electronic) protocols.
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Discuss any
adjustment to assay data.
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Historic:
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Due to the privatization of the laboratories in
the 1990s, a large part of the archive data was destroyed. As a
result, there is hardly any information about the standards used
and the control analyses determined. But corresponding results of
the control analyses and error estimates are documented in the
report.
Confirmation:
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Twinning of the previous Wismut drill hole S21
show acceptable reproduction in hole SaxDRE034.
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Results of Certified Reference Materials for Sn
show acceptable reproduction of certified values. Thus, analysis
method is assessed as appropriate to have produced reliable results
on a level of confidence required for resource
estimation
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Results of Blanks for Sn demonstrate that a
cross-contamination during sample preparation and analysis is not
observed.
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Internal quality control by ALS included the
following additional analyses: CRMs for each analytical method,
blanks and duplicate measurements of the drill core samples
submitted. Blanks: all analysed internal blanks had values of
<0.5 ppm Sn. Duplicates: all showed very good agreement for the
different analytical methods as shown in the following
plots.
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Location of data points
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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.
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Specification of
the grid system used.
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Quality and
adequacy of topographic control.
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All location information is in metric projected
coordinate reference system UTM ETRS89 Zone 33N as measured or
transformed from historic reference systems by Saxore.
Historic:
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In the 1976 to 1981 drilling campaign, drill
collars were surveyed in using a closed loop theodolite method tied
in to the national grid. It is uncertain if this method was used
for the earlier or later drilling campaigns.
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Downhole surveys for the early drilling were
measured using a Multigraph Inclinometer at 10 to 25m intervals.
This apparatus had an accuracy of 0.5° for the dip angle and 3° for
the azimuth. The final phase of drilling saw the use of camera
surveys although no details are known. All survey data in the
database were generated by using detailed surveyed points in
hardcopy level plans, which show accurate collar, downhole survey
and end of hole locations and RL (height above mean sea level) for
each of these points.
Confirmation:
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All drill holes are pre-planned and located by use
of a handheld GPS. Holes were originally sited and angled using
compass and clinometer. Prior drilling, hole collars were surveyed
with tachymeter from accurately surveyed official fixed-points due
to the lack of GPS signal and mobile connection. This was changed
to the use of Devico gyro navigation for the later downhole survey
in order to get an added level of accuracy.
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GEOPS carried out down-hole orientation surveys
with measurements at 25 m intervals, while Pruy KG measurement
spacing was approx. 50 m.
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Data spacing and distribution
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Data spacing for
reporting of Exploration Results.
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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.
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Whether sample
compositing has been applied.
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Historic:
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Drilling was done from 50 m spaced drifts in 10 m
distanced stations, each station having 1 to 3 holes drilled as fan
to the mineralization below or above the drift plus 5 m spaced
channels when the drift is intersecting the
mineralisation
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Predominant sample length is 1 m for both the
drilling and channels
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The data spacing and distribution is sufficient to
establish and suitably classify Mineral Resource
Estimates.
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For Sn a sufficient amount and density of data was
available in Hämmerlein to produce variograms in acceptable quality
for the domain of Skarn and Mineralised Schist. Thus, the resulting
parameters were used to interpolate Sn in domains of Skarn and
Mineralized Schist using OK for all the areas of Tellerhäuser
project area.
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For Fe2O3, Zn, Ag, Cu,
WO3, In, Bi, Ge, As, Cd IDW was applied due to limited
amount and distribution of these assays.
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Around 6 % (holes) and 3 % (channels) of sample
intervals are above 1 m. Thus, a sample compositing is
assumed.
Confirmation:
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The original drilling undertaken was intended to
be better than a 50m x 50m spacing.
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Twin drilling was used to verify the historical
drilling, check its geological units and verify the geochemical
results.
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The original data spacing is considered to be
sufficient to establish the degree of geological and grade
continuity appropriate for the JORC classifications
applied.
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Orientation of data in relation to geological
structure
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Whether the
orientation of sampling achieves unbiased sampling of possible
structures and the extent to which this is known, considering the
deposit type.
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If the
relationship between the drilling orientation and the orientation
of key mineralised structures is considered to have introduced a
sampling bias, this should be assessed and reported if
material.
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Historic:
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The drill orientation is approximately
perpendicular to mineralized skarn units and does not appear to
introduce bias.
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The schist mineralisation at Hammerlein has both a
sub-vertical and sub-horizontal component and hence the mainly
sub-vertical drilling may not be optimal for some of the
sub-vertical structures.
Confirmation:
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No orientated drilling was carried out.
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The skarn seams are sub-horizontal and the
drilling is angled at between -69° and -79° to be as close as
possible to cutting across the skarn seams at 90°.
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As drilling was designed to intersect the main
skarn seams at as high an angle as possible. The potential for any
introduced sampling bias is considered minor.
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Sample security
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The measures
taken to ensure sample security.
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Historic:
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This was an active uranium mining area during GDR
times and security was thus very tight. No reason to suspect any
security issues can be found.
Confirmation:
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All core and sample material was stored and
investigated in a locked facility. All transportation was done by
authorized personnel only. Sample transportation was cross-checked
by sample list completeness of amount of samples and sample
weight.
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Audits or reviews
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The results of
any audits or reviews of sampling techniques and
data.
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Historic:
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Audits and reviews were conducted at regular
intervals during the GDR era but results are not currently
available. The GDR era estimates are classified between C1 and
Delta category which require audits by the central
authorities.
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Audits and reviews have been done by HSC in 2019,
BARA in 2021
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The techniques of sampling, QA/QC methods and
quality of the historic data was assessed as appropriate to be used
for resource estimation
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