2010-12-17_REVISION - C1981019 ‎(115)‎

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 12/17/2010
• Doc Name: Exhibit 6 Item 7 Geology Pre-Feasibility Part 3
• Type & Sequence: PR3
• Media Type: D
• Archive: No

Rio Tinto Technical Services Limited RIO
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Lower Castle Street TINTO
Bristol BS99 7YR, UK
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Memorandum
To: Alan Jorgensen File: GBJ038
From: John.Forkes Copies: Bob Young, Juan Garcia,
Dwight Kinnes, Mike Whateley
Date: 27 July 2005
Geostatistical review of Collom drillhole data
Introduction
A geostatistical review of the Collom surface drillhole data was undertaken, the objective of which
was to ascertain if it was adequate for a pre - feasibility study. The data was supplied by Colowyo
• and processed by TS in Bristol. This memo summarises the work process and the results
obtained.
Data Used
The data supplied had been obtained from a series of surface diamond drills which had intersected
a series of coal seams, of which only the C, E and F seams were to be considered during this
study. The location of the drillhole samples used (by seam) is shown in figure 1. These suggest
that the drilling density is greatest towards the east, decreasing towards the west and north.
Seam Thickness
The histograms of seam thickness, by seam are shown in figure 2. A large spread of values is
noted in each case suggesting that each variable (sulphur, ash etc) should be considered with
respect to the length of sample from which that variable was obtained i.e. accumulations. Failure
to account for this volume /variance effect will lead to incorrect interpretations within the
geostatistical analysis. Hence all variables were converted to accumulations and these values
were subsequently used for the geostatistical analysis.
Geostatistical analysis
Semi - variograms are used to establish the spatial continuity between the sample data, which in
turn is used during the grade estimation (kriging) process. These were generated for thickness,
AFT (accumulation), ASH (accumulation), BTU (accumulation), MST (accumulation) and
SULPHUR (accumulation). The semi - variograms of thickness (figure 3) showed good structure
with low nugget effect and ranges between 5000ft and 10000ft.
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