annexc - Newmont Mining Corporation

Annex C3 – Geology and Geochemistry Supplemental Information C3 - 6
A summary of the Phase 1 results sorted by drill hole (borehole) are contained in Table
C3-2, which provides ANP, AGP, and NCV averages for each borehole, as well as averages
for the oxide and sulfide zones within each borehole. Average NCV for the sulfide zone (10
boreholes) are classified as basic (1-5 %CO 2) while the oxide zone (7 boreholes) NCV
averages range from inert to basic. The Phase 1 NCV classification shows little potential for
acid generation.
Based on the Phase 1 testing of 207 samples, The Company identified 4 major and 12 minor
waste rock types present within the mine pit. For Phase 2 of the geochemical testing
programme, The Company prepared 16 composite samples (rock mixed together from
multiple boreholes and depths) representative of each waste rock type to be encountered
during mining. The Phase 2 single rock-type composite samples were submitted for ABA
analyses, mineralogy and whole-rock metals. NCV results from Phase 2 were compared to
the Phase 1 data to confirm the previously assigned NCV classification for each of the 16
rock types. In addition, specialized tests were performed to further assess the potential for
acidity and metals release. Table C3-3 shows NCV results for the 16 composite samples,
summarized by borehole interval and rock type, as well as the Phase 1 static testing results
samples collected within the composite intervals.
Mineralogical data from the 16 composite samples show they contain up to 35 percent
carbonate minerals and as much as 2 percent of the predominant sulfide mineral pyrite
(Table C3-4), although arsenopyrite has been reported. Although carbonates have
potential to neutralize any acid that may be generated from weathering of the sulfides, these
carbonates primarily consist of up to 35 percent ankerite (a calcium-iron carbonate), which
dissolves to a lesser degree than pure calcium carbonate (calcite). The ankerite may have
less neutralization capacity than would be the case of the calcite were the carbonate mineral
present. Another factor contributing to the potential for acid generation is that the ankerite
contains iron, which can be slowly released during weathering to form iron hydroxide, and
in turn lower the pH.
Because of the presence of ankerite, described above, tests beyond the traditional ANP test
were performed to better predict potential for acid neutralization capacity. The Company
employed a hydrogen peroxide treatment to quickly oxidize the iron, correcting for
potential for released iron to precipitate as an iron hydroxide prior to testing the
neutralization potential. This acid neutralization potential acidity test (ANPA) was
performed on a weighted sulfide composite sample prepared for each Phase 1 borehole.
Table C3-2 shows the ANPA results. Calculating the NCV using the ANPA in place of
the ANP, results in slightly lower net neutralizing potential for the sulfide-zone sample, but
the NCV classifications remain basic (1-5 %CO 2). Thus, NCV values based on the ANPA
show that sulfide waste rock would have no tendency to produce acid.
Results of static acid-base accounting, including ANPA, are contained in Table C3-5 for the
16 Phase 2 composite samples. The major waste-rock types that contain sulfide (greywacke
and mafic volcanic) and oxide waste-rock type (saprolite) are represented by samples 1-4 in
Table C3-5. NCV classifications based on ANPA for both sulfide-containing rock types are
basic (1-5 %CO 2), indicating no potential for acid generation. The major oxide composite
(saprolite) is classified as slightly basic (0.1 to 1 %CO 2).
Akyem Gold Mining Project November 2008 FINAL EIS