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11.3
Cut-off thickness and insitu ash
Open cut Resources have been estimated
where thickness is greater than 0.3
metres and a raw insitu
ash below
Underground Resources have been estimated
where the insitu coal thickness
is greater than 1.5m. No ash
cut-
off has been applied as all reported seams have
low insitu ash (<~20% air-dried).
Underground Resources are
those that can potentially
be accessed from final
open-cut highwall using
a variety
of techniques including but not limited to board and pillar
mining techniques and highwall augering.
The split between open cut
and underground Resources has
been based on a 15:1
vertical insitu stripping ratio
(i.e. 15 bcm of waste
to one tonne of insitu
coal) as per previous
public Resource estimates. This
line has been
chosen as a
possible mining limit
considering the long-term
life asset of Curragh
assets and to
limit variation in
estimates from year to year based on short-term market
factors.
Deeper potential mineralization that
is poorly defined
through exploration or not
easily accessible from final
open-
cut highwalls has been excluded from the Resource
estimate.
11.4
Resources Exclusive of Reserves
Curragh tenements contain Resources
exclusive of Reserves which
have not been included
in the current mine
plan (
). Reasons that may preclude elevation
for Resources to Reserves
include, but are not limited
●
Insufficient
data
and/or
incomplete
technical
studies
to
justify
the
conversion
of
coal
Resources
to
●
Open cut Resources that may not justify conversion
to Reserves with current mining costs and/or
short-
term product price assumptions
Considering
the
long-life
of
Curragh
assets,
changing
technologies
and
varying
market
conditions
over
time
provide there will be an option to revise Reserves periodically.
11.5
Initial Economic Assessment
●
There are
380Mt of
Resource suitable
for open
cut mining
outside of
the reserves.
The cost
of mining
these Resources has been estimated using internal
cashflow models over the life of
mine plan, the cost
is estimated at
110
USD/product tonne (Prdt).
Product price was
estimated by creating
polygons of the
areas covered by the 380Mt of
Resource and using the simulation
grids in Vulcan to
estimate a primary
and secondary yield for the Mammoth, Mackenzie and
Pollux seams. These yields were then applied
to
a semi hard coking coal
and export thermal product
price. The resultant
product price was estimated
to
be 143
USD/Prdt and the margin 33 USD/Prdt.
●
There are 275MT of Resource suitable for underground
mining using the definition >15:1 stripping ratio.
The stripping ratio is a high
level cut off used to allocate
different seam mining thicknesses
for the open
cut and underground. The approach taken to estimate the
mining margin of these was:
a.
Estimate an average
mining cost using
Wood Mackenzie underground mining
costs, the average
cost of ten underground mines in Queensland was estimated
to be 90 USD/Prdt.
b.
Product price was
estimated by creating
polygons of the
areas covered by
the 275M Resource
tonnes and
using the
simulation grids
in Vulcan
to estimate
a primary
and secondary
yield for
the
Mammoth,
Mackenzie
and
Pollux
seams.
These
yields
were
then
applied
to
a
semi
hard
coking coal
and export
thermal product
price. The
resultant product
price was
estimated to
be
147 USD/Prdt and the margin 57 USD/Prdt.
11.6
Resource Classification and Estimate Uncertainty
Resource Classifications have been based on a borehole
geostatistical study conducted in 2020:
Curragh Drillhole Spacing Analysis Project; Resology
Pty Ltd; October 2020
