Black Bear Minerals (ASX: BKB) has increased the mineral resource estimate (MRE) for its Independence project in the US by 815,900 ounces to 2.2 million ounces gold equivalent (AuEq).
The new estimate comprises 5Mt at 6.29 grams per tonne gold for 1Moz (skarn, gold-only Inferred) and 89.9Mt at 0.42g/t AuEq for 1.21Moz AuEq (epithermal, Indicated and Inferred).
Chief executive officer Dennis Lindgren said there was significant growth potential outside these resources, with all mineral domains remaining open along strike and at depth.
He said Independence continued to demonstrate strong endowment, with the epithermal component spanning 1.5 kilometres of strike above the high-grade gold skarn.
Significant Growth Catalyst
The skarn mineralisation at Independence represents a significant catalyst for growth, particularly to the north where a historical drill hole intercepted similar mineralisation 580m outside of the current resource boundary.
The mineralisation is primarily hosted by calcareous conglomerate and sandstone within member units of the Battle Formation, where a review of historical drill core by Black Bear demonstrated gold mineralisation within the same host rocks.
The area represents a key target horizon for future drill testing spanning a strike length greater than the current mineral resource estimate.
Metallurgical test work by Black Bear on the skarn achieved gold recoveries of up to 95.9%, confirming that the mineralisation is non-refractory and amenable to conventional processing including gravity recovery followed by carbon-in-leach treatment, with low reagent consumption and very low concentrations of deleterious elements.
An earlier drillhole intersected high-grade mineralisation within the productive Harmony Formation, however a best intercept of 8m at 14.9g/t gold not included in the updated MRE provides the company with further scope to target extensions.
High-Level Epithermal Resource
From-surface gold-silver mineralisation at Independence hosted in the Pumpernickel Formation is characterised as a high-level epithermal system, developed as a leakage halo above the skarn.
Recent drilling focused on extensions of the epithermal resource in the northern half of the project area, as well as along the Rebel Trend to the east, resulting in the expansion of the epithermal portion of the resource from 419,600oz to the current 1.21Moz AuEq total.
This represents an increase of approximately 797,800oz (or 190%) on the epithermal MRE reflecting the identification of new mineralisation from extensional drilling, as well as the removal of an out-dated pit shell constraining the previous resource and new work on oxidation states and density values.
Black Bear believes further extension potential exists across multiple areas outside the epithermal resource, including along strike of the Rebel Trend, down-dip in the northern half of the project area, and below the drilled extents of the southern half.
Planned Metallurgical Testing
While historical metallurgical test work assessed the epithermal mineralisation for heap leach amenability, test conditions were optimised for oxide mineralisation only.
To date, no additional work has been completed to assess the optimised extraction of transitional and fresh material types.
Black Bear plans to carry out metallurgical testing across all oxidation states of epithermal material to determine the optimal processing flowsheet for oxide, transitional, and sulphide gold mineralisation.
The company also intends to increase the recovery of silver, which forms a substantial portion of the Independence resource.
The Independence project consists of 80 unpatented mining claims and 84 unpatented mill sites spanning approximately 1,861 acres in Lander County, NV, adjacent to the Nevada Gold Mine’s Phoenix operation about 16km south of Battle Mountain.
The project encompasses 470 acres of private fee surface land in the Battle Mountain mining district, where Black Bear holds exclusive water rights for future production wells.
