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Reference Material OxL25
Recommended Gold Concentration: 5.852 µg/g
95% Confidence Interval: +/- 0.048 µg/g
The above values apply only to product in jars or sachets
which have an identification number within the following
range: (The unique number range is not published on website)
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Prepared and Certified By: |
Malcolm Smith BSc, FNZIC
Malcolm Smith Reference Materials Ltd
2 Morriggia Place
Auckland 10
NEW ZEALAND
Telephone: +64 9 444 3534
Telefax: +64 9 444 7739
Email: mgs@xtra.co.nz |
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Date of Certification: |
12 December 2001 |
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Certificate Status: |
Original |
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Available Packaging: |
This reference material has been packed in wide-mouthed
jars that contain 2.5kg of product. The contents
of some jars may be subsequently repacked into sealed
polyethylene sachets. |
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Origin of Reference Material: |
Feldspars with minor quantities of finely divided
gold-containing minerals that have been screened to
ensure there is no gold nugget effect. |
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Supplier of Reference Material: |
ROCKLABS Ltd
P O Box 18 142
Auckland
NEW ZEALAND
Email: rocklabs@clear.net.nz
Telephone: +64 9 634 7696
Telefax: +64 9 634 6896 |
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Description: |
The component minerals have been
well mixed and a homogeneity test carried out after
the entire batch was packaged into wide-mouthed jars
to ascertain that the gold is evenly distributed throughout
the reference material. There is no soil component. The
product contains crystalline quartz and therefore dust
from it should not be inhaled. |
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The approximate chemical composition is:
(Uncertified Values) |
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% |
|
SiO2 |
67.83 |
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Al2O3 |
19.13 |
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Na2O |
10.69 |
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K2O |
0.28 |
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CaO |
0.50 |
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MgO |
0.17 |
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TiO2 |
0.06 |
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MnO |
0.01 |
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P2O5 |
0.13 |
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Fe2O3 |
0.60 |
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L O I |
0.41 |
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Intended Use: |
This reference material is designed to be included
with every batch of samples analysed and the results
plotted for quality monitoring purposes. |
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Stability: |
The container (jar or sachet) and its contents should
not be heated to temperatures higher than 50 °C. The
reference material is stable, with weight changes of
less than 0.5% at extremes of naturally occurring temperature
and humidity conditions. |
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Instructions for Use: |
Weigh out quantity usually used for
analysis and analyze for total gold by normal procedure. Homogeneity
testing has shown that consistent results are obtainable
for gold when 30g portions are taken for analysis. Homogeneity
cannot be guaranteed for gold if smaller weights are
taken for analysis. |
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Method of Preparation: |
Pulverized feldspar minerals were blended with finely
pulverized and screened, gold-containing minerals. Once
the powders were uniformly mixed the composite was
placed into 1162 wide-mouthed jars, each bearing a
unique number. 35 jars were randomly selected
from the packaging run and material from these jars
was used for both homogeneity and consensus testing. |
Homogeneity Test:
30g portions were selected as follows for homogeneity testing by an independent
laboratory.
Between Jar - Samples from the top of each of the
35 randomly selected jars.
Within Jar - The contents of three jars were
compacted by vibration (to simulate the effect of
freighting) and five samples removed successively
from top to bottom from each of the three jars.
Reference Group - 12 homogeneous sub-samples (ie
a control group) were prepared from one jar by taking approximately
400g and mixing by mat rolling, followed by coning and quartering
to obtain 30g (approximate) portions for gold analysis.
The Reference Group had an exceptionally low variance. The Between
Jar and Within Jar samples were therefore compared
with a similarly prepared reference group used for a pre-packaging
homogeneity test on this material. Statistical analysis
of the data indicated no significant difference in variability
between the pre-packaging reference group and all jar groups
of samples at the 0.05 level of significance. As
the homogeneity test was carried out using 30g analytical
portions, the same degree of homogeneity cannot be guaranteed
if smaller weights are taken for analysis.
Analytical Methodology:
Once homogeneity had been established, two sub-samples
were submitted to a number of well-recognized laboratories
in order to assign a gold value by consensus testing. The
sub-samples were drawn from the 35 randomly selected jars
and each laboratory received samples from two different jars. Indicative
concentration ranges were given. Two laboratories used
neutron activation and the remainder used fire assay for
gold analysis.
Calculation of Certified Value:
Results for gold were returned from 27 laboratories. Assessment
of each laboratory's performance was carried out on the basis
of z-scores, partly based on the concept described in ISO/IEC
Guide 43-1. Statistical analysis to identify outliers
was carried out using the principles detailed in sections
7.3.2 – 7.3.4, ISO 5725-2: 1994. Details of the criteria
used in these examinations are available on request. As
a result of these statistical analyses, six sets of results
were excluded for the purpose of assigning a gold concentration
value to this reference material. A recommended value
was thus calculated from the average of the remaining n =
21 sets of replicate results. The 95% confidence interval
was estimated using the formula:-
(where X is the estimated average, s is the estimated standard
deviation of the laboratory averages, and t is the 0.025
tail-value from Student's t-distribution with n-1 degrees
of freedom). The recommended value is provided at the
beginning of the certificate in µg/g (ppm) units. A
summary of the results used to calculate the recommended
value is listed on page 4 and the names of the laboratories
that submitted results are listed on page 5.
Legal Notice:
This certificate and the reference material described in
it have been prepared with due care and attention. However
ROCKLABS Ltd, Malcolm Smith Reference Materials Ltd and Tim
Ball Ltd accept no liability for any decisions or actions
taken following the use of the reference material.
Summary of Results Used
to Calculate Gold Value
(not related to order of laboratories listed)
Statistical analysis of both homogeneity and consensus test
results has been carried out by an independent statistician.
Participating Laboratories
Australia
Amdel Laboratories Ltd, Adelaide
Amdel Laboratories Ltd, Perth
Analabs Pty Ltd, Perth
Analabs Pty Ltd, Townsville
Becquerel Laboratories, Lucas Heights
Genalysis Laboratory Services Pty Ltd, Perth
Standard and Reference Laboratories, Perth
Brazil
Lakefield Geosol Limitada
Canada
Acme Analytical Laboratories Ltd, British Columbia
Activation Laboratories Ltd, Ontario
ALS Chemex, British Columbia
Bondar Clegg, British Columbia
Bourlamaque Assay Laboratories Ltd, Quebec
Chimitec Bondar Clegg, Quebec
Geoscience Laboratories, Ontario
Lakefield Research Limited, Ontario
Ireland
OMAC Laboratories Ltd
New Zealand
Amdel New Zealand Ltd, Otago
SGS New Zealand Ltd, Waihi
South Africa
Anglo American Research Laboratories (Pty) Ltd
AngloGold, Vaal River
AngloGold, West Wits
Lakefield Research Africa (Pty) Ltd
Mintek, Analytical Science Division
United States of
America
ALS Chemex, Nevada
Barrick Goldstrike Mines Inc, Nevada
Newmont Mining Corporation, Nevada
References:
For further information on the preparation and validation
of this reference material please contact Malcolm Smith.
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Certifying Officer |
Independent Statistician |
|
M G Smith BSc, FNZIC |
Tim Ball BSc (Hons)
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