Gold Ore Reference Material WG2
Recommended Value and 95% Confidence
Intervals
Gold concentration: 1.38 (+/-0.03) µg/g
0.040 (+/- 0.001) oz/ton
The above value applies only to sachets
which have a unique identification number within the
following range: (The unique number range is not
given on website for security reasons.).
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Prepared and Certified By: |
Malcolm Smith BSc, MNZIC
Laboratory Consultant
2 Morriggia Place
Auckland
NEW ZEALAND
Telephone: +64 9 444 7194
Telefax: +64 9 444 7739
Email: mgs@xtra.co.nz
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Date of Certification: |
8 August 1997
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Certificate Status: |
Final
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Available Sachet Types: |
This reference material has been packed in nominal
50g and 30g sized sachets and is sold with either a
Geocheck or Labcheck label.
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Origin of Reference Material: |
The source of this rock is a siliceous, oxidized
gold ore containing finely disseminated gold.
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Supplier of Reference Material: |
Rocklabs Ltd
P O Box 18 142
Auckland
NEW ZEALAND
Telephone: +64 9 634 7696
Telefax: +64 9 634 6896
Email: rocklabs@clear.net.nz
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Description: |
The rock which was taken from below ground level
and contains no soil component has been dried, crushed
and pulverized using a jet mill. This material contains
crystalline quartz and therefore should not be inhaled.
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The approximate chemical composition is:
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(Uncertified
Values) |
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% |
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SiO2 |
66.49 |
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Al2O3 |
14.91 |
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Fe2O3 |
5.52 |
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K2O |
2.72 |
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CaO |
1.47 |
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MgO |
0.74 |
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TiO2 |
0.54 |
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Na2O |
0.30 |
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MnO |
0.21 |
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P2O5 |
0.07 |
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L.O.I |
6.35 |
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Intended Use: |
This standard is designed for every batch use for
quality monitoring purposes.
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Stability: |
The sachet and its contents should not be heated
to temperatures higher than 80°C. The sachet
is made from a polyethylene/aluminum foil/paper
laminate and is water resistant. The reference
material inside is likely to last indefinitely.
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Instructions for Use: |
Cut open sachet.
Do NOT dry before weighing.
Weigh out quantity normally taken for
analysis.
Assay for gold by usual procedure.
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Method of Preparation: |
The originating rock was ground extremely fine
by jet milling in order to obtain an even distribution
of finely divided gold particles. (The starting
material already contained finely disseminated gold.)
Following jet milling and equilibration the entire batch
was mixed using a rotary mixer and blending operation.
The material was then placed into sachets. Approximately
6500 30g sachets and 4300 50g sachets were prepared.
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Particle Size: |
The particle size distribution of the reference
material is as follows:
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% |
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>75 µm |
0 |
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63 - 75 µm |
0 |
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45 - 63 µm |
0 |
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33 - 45 µm |
0 |
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25 - 33 µm |
0.44 |
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18 - 25 µm |
3.18 |
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13 - 18 µm |
7.36 |
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<13 µm |
89.0
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Homogeneity Test: |
68 sachets (equal to greater than three times the
cube root of the total number of sachets produced, including
both 30 gram and 50 gram sachets) were sampled at
regular intervals from the packaging run. These
were analyzed and the results compared
with a batch of 12 sub-samples of the same
raw material which had been ground in a
Rocklabs ring mill, mixed by mat rolling and coned
and quartered to obtained 30g portions for analysis.
The ratio of the variances of the two groups was
compared to the relevant F value at the 95% level
of probability. The conclusion of the comparison
was the acceptance of the null hypothesis
of no difference between the groups. The
homogeneity test of the reference material
in its packaged form is based on 30g analyses. If
smaller portions are taken for analysis the same degree
of homogeneity can not be guaranteed.
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Analytical Methodology: |
Once homogeneity had been established two sachets
(one 30g and one 50g ) were submitted to 19 well established
laboratories in order to assign a gold value by
consensus testing. Each laboratory was asked
to carry out the analysis by fire assay
and to analyze only 30g portions from each
of the two sachets.
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Calculation of Certified Values: |
19 sets of results were returned. Cochran's and
Grubbs statistical tests were applied. No outliers were
identified as a result of these tests. The assigned value
was calculated from the unweighted mean of the averages
of the 19 sets of replicate results. The 95 % confidence
limits were calculated from the standard deviation
of the 19 averages. The assigned value is provided
at the beginning of the certificate in both µg/g
(ppm) and oz/ton units.
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Participating Laboratories
Australia
Amdel Laboratories Ltd, Adelaide
Amdel Laboratories Ltd, Perth
Analabs Pty Ltd, Perth
Assaycorp, Pine Creek
Australian Laboratory Services P/L, Brisbane
Enviromet Operations Pty Ltd, Sydney
Genalysis Laboratory Services Pty Ltd, Perth
Canada
Acme Analytical Laboratories Ltd, Vancouver
Activation Laboratories Ltd, Ontario
Chemex Labs, Vancouver
Intertek Testing Services Bondar Clegg, Vancouver
XRAL Laboratories, Ontario
New Zealand
Grayson Laboratories Ltd, Otago
SGS New Zealand Ltd, Waihi
United Kingdom
Anamet Services (Rio Tinto), Bristol
United States
of America
Barrick Goldstrike Mines Inc, Nevada
Chemex Labs, Nevada
Cone Geochemical Inc, Colorado
Newmont Gold Company, Nevada
Legal Notice
This certificate and the reference material described
in it have been prepared with due care and attention.
However Rocklabs Ltd or Malcolm Smith accept no liability
for any decisions or actions taken following the use
of the reference material. Our liability is limited
solely to the cost of the reference material.
References
For further information on the preparation and validation
of this reference material please contact Malcolm Smith.
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Certifying Officer |
Checked by Independent Statistician |
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M G Smith BSc, MNZIC
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D Tebbutt BSc
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