Great Basin Gold Revises Hollister Mineral Resources Based On Trial Mining & Drilling Results: Gold Equivalent Ounces Increase B
June 17 2009 - 9:59AM
PR Newswire (US)
VANCOUVER, June 17 /PRNewswire-FirstCall/ -- Great Basin Gold Ltd.
("Great Basin Gold" or the "Company"), (TSX: GBG; NYSE Amex: GBG;
JSE: GBG) announced today that a revised mineral resource estimate
had been completed for the Company's Hollister Project on the
Carlin Trend in Nevada, USA. The overall contained gold equivalent
ounces at Hollister have increased by 27% from 2.3 million in June
2008 to 2.9 million(1). At a cut-off grade of 0.25 oz/ton (8.57 g/t
Au), the combined measured and indicated mineral resources contain
1.45 million gold equivalent ounces grading 1.167 oz/ton (40.00
g/t) for gold and 8.59 oz/ton (295 g/t) for silver. A further 1.43
million gold equivalent ounces are contained in inferred mineral
resources of 1.03 million tons at a grade of 1.340 oz/ton (45.95
g/t) for gold and 2.72 oz/ton (93 g/t) for silver; gold equivalent
ounces in the estimated inferred resources increased 111% from June
2008. The resource estimate has benefited significantly from over
nine months of trial mining, which generated data from channel
sampling and delineation drilling for stope development. As a
result of the integration of empirical data from geological
observations and ore control sampling into the vein model, more
stringent parameters have been applied to measured and indicated
classifications. In addition, 161 additional boreholes (totaling
51,430 feet) completed in the period from April 2008 to March 31,
2009 were integrated into the model. The drilling program, mostly
conducted from underground, has provided infill data to delineate
stopes for trial mining, and significantly improved our
understanding of the lateral and vertical geological continuity of
the vein system. The resource estimate reflects depletion of
material mined in 2008 and 2009 (up to March 31 2009), totaling
103,746 gold equivalent ounces at an average grade of 1.55 oz/ton.
Results of the resource estimate based on all drilling and ore
control channel sampling to March 31, 2009 are tabulated below.
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Contained Resource Cut-off Au Au Au Category oz/ton Tons Tonnes
oz/ton g/t oz(2)
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Measured 0.25 199,300 180,800 1.895 64.98 377,700
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Indicated 0.25 911,900 827,200 1.008 34.54 918,700
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Total Measured & Indicated 0.25 1,111,200 1,008,000 1.167 40.00
1,296,400
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Inferred 0.25 1,035,300 939,200 1.340 45.95 1,387,500
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--------------------------------------------------- Contained
Contained Resource Ag Ag Ag Au Category oz/ton g/t oz(2) eq oz(1)
--------------------------------------------------- Measured 29.02
994.8 5,782,800 468,100
--------------------------------------------------- Indicated 4.13
141.5 3,763,300 977,500
--------------------------------------------------- Total Measured
& Indicated 8.59 294.6 9,546,100 1,445,600
--------------------------------------------------- Inferred 2.72
93.2 2,815,400 1,431,500
---------------------------------------------------
--------------------------------------------------- (1) Gold
equivalent ounces (Au eq oz) were calculated by using the following
metal prices: US$800/oz for Au and US$12.5/oz for Ag. (2)
Metallurgical recoveries are not applied to resource values.
Contained metal estimates assume 100% recoveries. Some figures may
not add due to rounding. The total estimated measured and indicated
mineral resources prior the depletion from trial mining was 1.549
million gold equivalent ounces and is comparable with the 1.569
million gold equivalent ounces in 1.615 million tons grading 0.87
oz/ton (29.71 g/t) Au and 4.57 oz/ton (156.68 g/t) Ag at a 0.25
oz/ton cut-off announced in June 2008. There are internal
differences to the current and 2008 estimates, which are mainly
related to modifications to resource estimation procedures
described below: - Empirical geological measurements have confirmed
the previous model over estimated the width of the veins, hence,
tons were over estimated tons but, at the same time, grade was
under estimated. The current estimate utilises an improved method
for modelling the veins (a mathematical algorithm with a minimum
tolerance of a 6" vein width) and, coupled with a partial
percentage estimate, has led to a higher accuracy in estimating the
volume from the wire-frame model of the veins; - Grade
interpolation within the vein wire-frames was done using Inverse
Distance Squared statistics in the current estimate (instead of
Ordinary Kriging geo-statistics); - Search radii utilized to
categorize the confidence of grades within the vein wire-frames
were decreased (100 feet/30 meters for measured and 280 feet/85
meters for indicated) and the average distance of informing samples
was introduced, which increased the stringency for the measured and
indicated categories; and - The minimum number of samples to inform
a given block was increased to 3 (compared to 2 in the previous
estimate). The outcome of these changes is a more conservative
approach to resource classification that more closely reflects what
is observed empirically underground. Consequently, the tonnage in
the measured category has decreased but grade has increased.
Tonnage in the indicated category has increased due to
reclassification and tonnage in the inferred category has increased
due to re-classification and additional drilling testing the extent
of mineralization. As the mine development progresses, the
evaluation and upgrade of the mineral resources from the inferred
and indicated to a measured category will provide data to assess
the potential for reducing cut-off grade. Also the current testing
of various mining technologies may reduce stoping costs, and expand
the opportunity to exploit certain narrow veins that would
otherwise not be considered in the mine plan. Employing a lower
cut-off grade would allow lower grade material in the indicated
category to be included in the resource. The depth extent of the
vein system is yet to be fully established, therefore, to be
conservative, inferred resources have been constrained to a depth
of 4,350 feet (1,318 meters) above mean sea level (approximately
1,200 feet or 380 meters below surface). Certain areas of previous
indicated resource have also been re-categorized into inferred
because of lesser density of sampling data. Inferred resource
grades have increased from 0.510 oz/ton to 1.34 oz/ton for gold and
1.43 oz/ton to 2.72 oz/ton for silver due to the localized
extrapolation of well defined areas of higher grade pay shoots in
the measured and indicated categories. There is a noticeable
decrease in silver grades from measured to inferred categories
which reflects the occurrence of the Ag-selenide naumanite in the
well drilled and sampled high grade shoots as opposed to lesser
borehole data in the inferred zones. The lack of sample density in
the inferred material underpins the lesser confidence in the
resources in this category. The ongoing program will continue to
focus primarily on extensions of the Gwenivere and Clementine vein
system to the west/northwest and at depth. Also, further
investigation of Blanket zone mineralization hosted in Tertiary
volcanics above the Gwenivere/Clementine vein system is planned.
Detailed reassessment and modeling of all Blanket zone
intersections is currently underway, as there is potential for a
significant resource in this area as indicated by previous surface
drilling. The Company currently has three drill rigs in operation
underground, undertaking stope delineation, resource infill and
exploration drilling. Surface exploration is currently focused on
collating and reviewing all geophysical, geological and drilling
data for the property, with the intent of better delineating
basement structures that control mineralisation. Additional
drilling is also being considered for the Hatter Graben area (press
release January 29, 2009) during the third and fourth quarters of
2009. Ferdi Dippenaar, President and CEO, commented: "Our ongoing
exploration drilling programs and results from trial mining
continue to confirm the prospectivity of the Hollister property,
evidenced in the substantial increase in the reported resources.
The tighter geological controls constraining the estimate are also
improving trial stope tonnage and grade estimates and, as a
consequence, our mine planning is benefiting from more accurate
information. As the underground development continues, there will
be further opportunities to drill test the depth extensions of a
number of high grade zones that are emerging from the evaluation.
The continued exploration drilling from underground is bearing
success with tracking the lateral extensions of the Hollister veins
both eastward towards Hatter Graben, but also stepping
northwestward into the major Butte Fault bounding structure.
Furthermore, the review of Blanket style mineralization in the
overlying volcanics may provide an interesting upside to the
current resource profile, as it could be mined from the current
infrastructure." The mineral resources reflect an in situ vein
model, and tonnages and grades were estimated by using a
combination of a partial percentage block model and constrained
inverse distance statistics. There is no mining dilution included
within the vein model. The estimates were completed by Dale
Richards, Pr.Sci.Nat., Great Basin Gold's Group Mineral Resource
Geologist, and signed off by Phil Bentley, Pr.Sci.Nat., Great Basin
Gold's Vice President: Geology & Exploration, a Qualified
Person as defined by Canadian Securities Regulations in National
Instrument 43-101, who has reviewed and approved the information
and this news release. Details of the estimate will be included in
a technical report filed on http://www.sedar.com/ in 45 days. Ferdi
Dippenaar President and CEO
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Samples collected from the Hollister Development Block Project are
delivered to Inspectorate America Corporation (Inspectorate) in
Sparks, Nevada. Vein samples are analyzed by standard fire assay
procedures. For standard fire assay, vein sample preparation
consists of drying and jaw- crushing the entire sample to 90%
passing 10-mesh, taking a 300 g sub- sample using a Jones splitter,
and then pulverizing the 300 g sub-sample to 90% passing 150-mesh
using a large capacity ring and puck pulverizer. A 30 g charge is
fire assayed. All metal determinations are by gravimetric finish.
Laboratory Quality Assurance/Quality Control (QA/QC) is monitored
using coarse reject blanks and assay standards, duplicate fire
assays, and Inspectorate's internal standards and blanks. Coarse
blanks (barren rhyolite or landscape marble) and assay standards
are inserted into the sample sequence as blind samples prior to
submitting the samples to the laboratory. Inspectorate also inserts
assay standards and blanks into the sample stream. QA/QC results
are within acceptable limits.
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No regulatory authority has approved or disapproved the information
contained in this news release. This release includes certain
statements that may be deemed "forward-looking statements". All
statements in this release, other than statements of historical
facts, that address possible future commercial production, reserve
potential, exploration drilling results, development, feasibility
or exploitation activities and events or developments that Great
Basin Gold expects to occur are forward-looking statements.
Although the Company believes the expectations expressed in such
forward-looking statements are based on reasonable assumptions,
such statements are not guarantees of future performance and actual
results or developments may differ materially from those in the
forward-looking statements. Factors that could cause actual results
to differ materially from those in forward-looking statements
include market prices, exploitation and exploration successes,
continuity of mineralization, uncertainties related to the ability
to obtain necessary permits, licenses and title and delays due to
third party opposition, geopolitical uncertainty, changes in
government policies regarding mining and natural resource
exploration and exploitation, and continued availability of capital
and financing, and general economic, market or business conditions.
Investors are cautioned that any such statements are not guarantees
of future performance and those actual results or developments may
differ materially from those projected in the forward-looking
statements. For more information on the Company, Investors should
review the Company's annual Form 40-F filing with the United States
Securities and Exchange Commission and its home jurisdiction
filings that are available at http://www.sedar.com/. Information
Concerning Estimates of Measured, Indicated and Inferred Resources
This news release also uses the terms "measured resources",
"indicated resources" and "inferred resources". The Company advises
investors that although these terms are recognized and required by
Canadian regulations (under National Instrument 43-101 Standards of
Disclosure for Mineral Projects), the U.S. Securities and Exchange
Commission does not recognize them. Investors are cautioned not to
assume that any part or all of the mineral deposits in these
categories will ever be converted into reserves. In addition,
'inferred resources' have a great amount of uncertainty as to their
existence, and economic and legal feasibility. It cannot be assumed
that all or any part of an Inferred Mineral Resource will ever be
upgraded to a higher category. Under Canadian rules, estimates of
Inferred Mineral Resources may not form the basis of feasibility or
pre-feasibility studies, or economic studies except for Preliminary
Assessment as defined under 43-101. Investors are cautioned not to
assume that part or all of an inferred resource exists, or is
economically or legally mineable. DATASOURCE: Great Basin Gold Ltd.
CONTACT: For additional details on Great Basin Gold Ltd. and its
gold properties, please visit the Company's website at
http://www.grtbasin.com/ or contact Investor Services: Tsholo
Serunye in South Africa 27 (0)11 301 1800; Melanee Henderson in
North America 1-800-667-2114; Barbara Cano at Breakstone Group in
the USA (646) 452-2334
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