Company: CENX
Filing Date: 2025-03-03
Form Type: 10-K
Source: 0000949157-25-000024
Chunk: 65

Company: CENTURY ALUMINUM CO
Filing Date: 2025-03-03
Form: 10-K
Item: Item 2
Chunk 65
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%1.06 %Inferred mineral resources— — %— %— %

(1)Represents the Company's 55% interest in the above-quoted mineral resources. The reference point for the mineral resource is the in situ predicted dry tonnage.

(2)Available Alumina at Low Temperature

(3)Reactive Silica

(4)Phosphorous

Cut-offs are based on a 35% AvAl2O3 grade for the overall pit. The exception is Porus Victoria Township location where the value of this bauxite for blending allows for a cut-off of 30% AvAl2O3 to be applied. ReSiO2 grades should not exceed 6% on a pit basis; where high silica zones are encountered in mining such bauxites are flagged and are to be avoided in the extraction process. P2O5 and goethite-hematite ratios are monitored for blending purposes, however no specific cut-offs are applied to constrain the resources.

No call factors are applied to the above resource tonnages and grades. Metallurgical recovery is approximately 84% but has not been applied to these tonnages. The bauxite transfer price to the refinery is $12.46 per tonne and tonnage is reported on a bone-dry basis. All resource estimation is based on an in-situ density of 1.44 tonnes/m3.

29

The Company does not have mineral resource information at December 31, 2023 or December 31, 2022 for comparative purposes.

Refer to the Jamalco TRS in Section 11 for more information on the mineral resource estimates, including key assumptions used.

Exploration Activity

Exploration at the property is completed using auger drilling. Deposits are identified by the slight topographic depressions across the limestone relief suggesting the potential for karst hosted bauxite mineralization. Aerial survey assists in the selection of potential deposits and a few prospecting auger holes allow for confirming the exploration target. At the start of operations, much of the area was owned by the government or by Jamalco and the local communities were less sensitive to bauxite development. Currently, the ownership of land parcels requires Jamalco to obtain sufficient rights before exploration is completed. Recent exploration has not been material to operations.

The following table shows a summary of the deposits, drill holes, and assays completed at the property as of September 30, 2024:

DepositsHolesM