I'm not going to tell anyone to disregard your posts Blairman, only because I think it's good to have everyone read them so they can see how you are selective with material.
Here's the full PFS section on the grades used in the pilot testing by Kemetco.
Are there any grades less than 3.5% Mn that were used? None that I can see. Average grade at AP is 2.5% I believe. And yes, the McGregor Pit ore was used along with ore from the Chapin Wash mineralogy.
Seems to me that they tested ore as low as 3.5% Mn, and then extrapolated results down to 2% without running the lower grade representative ore from AP. Any comments?
13.3.1 SAMPLE CHARACTERISTICS
Bulk samples, collected from two locations across the face of CWH in the upstream
part of the Chapin Wash, arrived at the start of 2011 in 25 steel drums, weighing
about 7 t in total (Kemetco 2011). Three randomly selected drums were prepared for
the test program; their contents were very consistent in grade and particle size
assays. Typical blends of materials requiring size reduction contained approximately
50% mudstones and rocks up to 10" in size. Materials were crushed to a top size of
½". Assays are compared in Table 13.2, showing that the three CWH drums
selected for batch testing were homogeneous in makeup. Random samples of
MacGregor pit (MGP) material that were also tested showed higher grades of
manganese, but otherwise very similar feldspar-dominated compositions.
Test charges were subjected to dry milling, yielding pulps finer than 4 mm after very
short grinding times. The Bond rod mill index of 6 kWh/t confirmed the soft nature of
the material, with a negligible abrasion index (<0.09 g) on the more competent
specimens that were used for hardness testing (Kemetco 2011c; Kemetco 2011d;
Hazen 2011). Crushing tests were conducted with different types of equipment to
verify that the materials were soft, non-abrasive and free-flowing (Kemetco 2012b).
Table 13.2 Relevant Feed Assays of Materials Tested for Proof of Concept
by XRF
Sample Name SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O TlO2 MnO P2O5 BaO LOI Total
CWH Drum A 54.68 13.57 5.34 1.72 1.90 1.02 5.63 0.57 4.50 0.16 0.56 8.47 98.26
CWH Drum B 55.13 13.79 5.46 1.14 1.91 0.93 6.01 0.59 4.60 0.16 0.50 8.25 98.63
CHW Drum C 55.65 12.07 4.34 3.03 1.76 1.36 4.38 0.48 4.07 0.14 0.98 10.00 98.55
MGP Met 4 58.54 13.28 4.51 1.43 1.64 1.75 5.18 0.55 4.78 0.16 0.65 5.63 98.28
MGP Met 2 54.43 11.87 3.81 2.89 1.42 1.42 5.09 0.45 7.38 0.13 0.90 7.99 98.36
MGP Met 1 56.35 10.90 3.14 2.71 1.16 1.69 4.57 0.39 8.83 0.14 1.32 6.95 98.42
In summary, testing since the 1930s has confirmed the remarkable uniformity of
Artillery Peak materials that respond very well to aqueous sulphur dioxide leaching.
Based on the Kemetco tests on Chapin Wash materials ranging from MGP grading
10.5% Mn down to CWH of 3.5% grade, a conservative depletion to 0.2% Mn in the
leach residues is readily achieved. This forms a reliable basis for grade-sensitivity
estimates as illustrated in Figure 13.1 where extractions >85% Mn can be expected
for materials grading as low as 2% Mn under baseline non-optimized conditions.
