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is to assess the acid generation and neutralization potential of the material; to evaluate its
potential for metals and radioanalyte leaching; and to facilitate long-term predictions of water
quality associated with the Waste Rock Facility and pit wall water effluents. Both waste rock and
pit wall surfaces have the potential to impact water resources due to oxidation and dissolution of
a variety of mineral phases. Material excavation and stockpiling results in physical grain size
reduction and an increase in the rock surface area exposed to the atmosphere, which enhances
the natural weathering processes. Additional detail on waste characterization is provided in
Section 5.3.1.6, below.
4.5.4.3 Upgrading – PUG Plant
The PUG Plant is designed to maximize concentration of the rare earth minerals and produce a
mineral concentrate. The PUG process employs a series of crushing, attritioning, washing,
screening, and gravity methods to concentrate the rare earth-bearing fines and reduce the
physical mass. There are areas of the Mineable Pit that contain variable amounts of weathered
oxide ores or OxCa ores, and that contain variable grades of stockwork mineralization adjacent
to the higher grade ores. Each of these ore types has a different upgrade percentage and mass
reduction in the PUG circuit.
The mining plan will encounter a distinct high grade zone early in the project which will allow for
preferential mining for a period of 9 years. Low and mid-grade ores will also be mined and
stockpiled for future PUG processing. The PUG circuit has been designed to process up to 500
tons per day of high grade oxide and up to 1,000 tons per day after Year 9 (depending on ore
variability) of OxCa stockwork and low grade ores, which will be blended to meet mine pit
production plans and market demands. In Year 10, the production rate in the PUG Plant will
increase up to 1,000 tons per day of ore and will produce up to 600 tons per day of bulk mixed
rare earth carbonate pre-concentrate. The PUG processing strategy is to maximize the rare
earth grade and recovery, and minimize the mass or tonnage of the pre-concentrate that is
transported to the Hydromet Plant. Stockpiled ores will continue to be PUG processed up
through Year 43 when they are estimated to be depleted. Reclamation of mining facilities will
begin as soon as the mineable ores are depleted. Conceptual process flow sheets for the PUG
Plant are provided in Appendix E. The pre-concentrate will be transported by haul trucks to the
Hydromet Plant.
Feedstock.
The PUG Plant will have the ability to process up to 500 dry tons per day of ore
from the mine, depending on ore variability during the first 9 years of the project. There are
several categories of material (Bull Hill Oxide High Grade and OxCa and Whitetail Oxide and
OxCa). The oxide (global) high grade, OxCa, and Whitetail ores will be stockpiled at the PUG
Plant while the stockwork and low grade ore will be stockpiled in the Low Grade Ore Stockpile
or in the Waste Rock Facility. The rejected coarse rock (run of mine) from primary and
secondary crushing and screening, along with gravity/magnetic reject separated from the ore,
will be transported from the PUG Plant to the Waste Rock Facility in end dump trucks via a Mine
Area haul route.
Up to 260 pounds per day of a non-toxic flocculent will be added, based on the production rate,
to increase the separation efficiency of the solid particles from the water medium. A medium to
high molecular weight, non-ionic polyacrylamide (long chain hydrocarbons with amino groups
attached) flocculent will be used. The flocculent consumption rate will be approximately 0.34
pounds per ton of dry pre-concentrate thickener feed. The Material Safety Data Sheet for a
typical flocculent that may be used (Hyperfloc©NF301) is included in Appendix L.
Water and power requirements for the PUG Plant and other required utilities are discussed in
Section 4.7.1, Utilities.
