The entirety of Mosaic’s mineral reserves and resources exist within sedimentary deposits. Economic phosphorite exists in a matrix of gravels, sands, silts and clays that are readily extractible. These economic deposits overlay a carbonate platform where phosphorite is absent. The bedrock and economic matrix are overlain by sands, clays and silts that are easily removed. Limitations of extraction arc the case of excavation, the capacity of the matrix to slurry, the grade of the phosphorite, gangue minerals, the depth of the matrix, and the overburden to be removed.

Deposition of phosphorite occurred in the Miocene and Pliocene epochs. The depositional environment was shallow marine with sea levels of 300 ft. (100 m) or less. Cold phosphate rich waters were upwelled and mixed with warm surface waters creating vigorous biologic activity. Biological remains settled on the sea floor in regional anoxic zones. Phosphate subsequently substituted into calcium carbonate in the form of the mineral francolite. Accessory- mineralization does occur, but it is of little economic consequence. The deposit underwent transport and rework through marine winnowing. Post-depositional rework is extensive and site factors such as hydrology and groundwater geochemistry influence grade and gangue mineralization.

Gangue minerals are generally limestone, dolomitic limestone, iron concretions of varying sizes and competent clays that resist disaggregation by washing. Limestone, dol ........

Four Corners is a phosphates production stage mining facility. Phosphate is extracted using surface mining techniques. Mining is utilizing electric walking draglines to remove overburden and mine the phosphate ore (matrix). The matrix is hydraulicaly transported to the benefication plants via a series of centrifugal pumping systems.

Draglines utilize a one-pass. modified simple side-cast method for overburden removal and mining of matrix. Overburden will be spoiled on top of the ground, in an adjacent mined out cut or pumped, depending on overburden matrix thickness and available area. Geological considerations such as overburden matrix thickness, spoil stacking characteristics and dragline reach arc considered in cut design to ensure spoiled overburden does not encroach on uncovered matrix.

Regardless of the cut type and spoil placement, matrix is mined in a consistent manner. An earthen well is formed with earthmoving equipment outside of the dragline cut but within the dragline dumping radius. After the dragline uncovers an advance of approximately 50 ft. (16 m). matrix is mined and placed in the well where it is slurried with 10.000 US gpm of water at high pressure (250 to 3(X) psi). Once all matrix is mined, the dragline walks back and repeats the process. While the dragline generally advances in one direction the tub follows an arc within the cut as the dragline is dumping matrix to a fixed location. Once the dragline advances past the reach of th ........

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