nachingwea nickel tenor much higher

While similar ultramafic complexes, such as
the Thompson Nickel Belt in Canada, generally contain nickel tenors (the amount of nickel
in 100% sulphides) of 4-8.5% nickel, Ntaka
Hill tenors are much higher: 6-13% nickel in
the magmatic zones and 10-17% in the remobilised zones.
A portion of nickel at Ntaka Hill is hosted
in pyrrhotite but around 90% is hosted in
pentlandite, the sulphide mineral most conducive to high tenors. Its coarse grain size also
makes it amenable to less-intensive grinding
requirements.
The discovery of high nickel tenors due to
the extensive presence of pentlandite proved
to be a defining moment for the project.
Speaking at the Australian Nickel Conference in October, IMX general manager projects, Stewart Watkins, said despite being a
process engineer with more than 20 years’
experience he had rarely seen such amenable material.
“When I first looked at this project the metallurgy jumped out at me,” Watkins said. “In
our first test we got 80-90% recoveries to a
14-19% concentrate, mainly because of the
high nickel tenors, and that is without doing
anything complicated.
“The MgO is not a problem. You just have to
float the sulphides and even on the low-grade
material we are producing an 11.5% concentrate with 70% recoveries.”
This understanding has opened up the project area to an array of new interpretations.
No longer is grade the indicator; it is now
tenor that is vital.
“It all comes down to nickel tenor,” as
Katchen has it.
Tirschmann, Katchen and the entire exploration team are now re-examining historical
core to identify where the highest tenors are
located. It is into this reimagining of Ntaka Hill
that IMX’s new general manager exploration
and business development, Africa, Mike Hannington, has stepped.
“I quickly realised it is no longer the EM that
is drilling this project and it is ready for some
fresh impetus,” Hannington said on his fourth
visit to site. “With new eyes you get new ideas
and we need to integrate the geophysics, the
geochemistry etcetera to build a total picture
of the Ntaka Hill intrusion.