Ann: March 2021 Quarterly Activities and Cashflow Report, page-140

Hi Squash

The ARL announcement from 21/02/2021 provides clarity on this issue:
GNCP High Grade Resource - 60 million tonnes at 1. 0% nickel Sustainable Long Long-life Battery Metal Resource Confirmed

Almost all Ni/Co/Mn is within the premium Clay Upper Goethite (CUG) zones which have low Mg/Al levels.

There are detailed figures regarding material type classification and their Mg, Al and Fe levels. These elements directly affect the acid consumption (Mg, Al) and acid regeneration (Fe) during HPAL. Low Mg/Al ore with high Fe content is ideal for low acid consumption (opex).

Global Mining Research:
Aside from nickel grades, the main consideration in HPAL is the amount of acid consuming agents in the autoclave feed, with sulphuric acid representing the biggest component of opex. Leaving aside iron (which reprecipitates as hematite, regenerating acid), the principle acid consuming elements are magnesium and aluminium.
In general, acid consumption (kg/t ore)=55+36.1(Mg)+28.8(Al) or on average 260-400 kg/t at existing operations.
This equation dictates why you want an autoclave feed which is generally sub 5% Mg, largely precluding saprolite feeds.

Below is an example for the Goongarrie South (GS) resource. Almost all the good stuff is in the orange zone with low Mg (<3%) and Al and high Fe.

Notably, 15 tonnes of the below GNCP core material and ancillary drill material were processed in a pilot-scale HPAL circuit (Simulus) to produce Mixed Sulphide Product (MSP, >95% recovery in continuous piloting) and Ni/Co sulphate (SGS Australia).

Don't let unsubstantiated claims of an anonymous, self-proclaimed expert get in the way of facts as per ASX announcements.


Explanatory Discussion:
•The blue shaded rows are overburden to the goethite-hosted mineralisation, being P as in Pedogenic (Quaternary-agedsoil profile), AL as in Alluvial and AC as in Alluvial or lacustrine Clay (both related to the Tertiary-aged ancestral LakeGoongarrie), LA as in Laterite (Tertiary-aged weathering surface).
Their metallurgical performance will not match the premium goethite mineralisation, but resource tonnes are not significant.
•The orange shaded rows are the premium Clay Upper Goethite (CUG) mineralisation material types, with variously K being kaolinite, Z being asbolite, F being ferruginous - haematite, magnetite, maghemite, and S silica.
Bench-scale metallurgical performance of CUG Material Types is excellent with good rheology and low acid consumption(refer GNCP PFS ASX announcement, 28 March 2018). Most importantly, the Material Types demonstrate a premium mineralogical assemblage in terms of uniformity and hence ability to schedule production with consistent Material Type plant feed.
•The yellow shaded row represents Clay Lower Goethite Serpentine (CLGE) and manifests in drilling as a lighter hue in RC drill chips, reflecting the initial occurrence within the 0.5% Ni cut-off wireframe of magnesium, with a consequent increase in autoclave acid requirement.
Clay Lower resource tonnes are not significant at GS.
•The green shaded rows represent Saprock (SR) with variable E being Serpentine, S being weathering zone silica, B being the weathering zone carbonates dolomite and magnesite, generally light grey and green hues in RC drill chips, reflecting the occurrence within the 0.5% Ni cut-off wireframe of dolomite and magnesite carbonates. As acid consumers, the saprock is excluded as an autoclave feed, but is an excellent neutraliser acid consumer.