The Chapadão pit is located in the carbonated complex designated as Domo I (o Complex Catalão I), which belongs to the Igneous Province of Alto Paranaiba. The area is characterized by a weathering profile developed in an intrusive lithology which consists of five types of materials: fresh rock, altered rock, saprolite (two types), and lateritic soil cover.

Catalão I complex
The phoscorite-carbonatite complex Catalão I is an approximately 5 km diameter circular structure. Within this complex, rocks were concentrically emplaced, with a predominant carbonatitic rock core which is surrounded by phoscorites and in turn surrounded by silicate rocks, such as pyroxenite. The rock types are closely associated with the mineralisation in the complex with niobium mineralisation located in the core of the complex (in the phoscorite-carbonatite zone) which is in turn surrounded by high-grade phosphate mineralisation (phoscorite zone) followed by the outer low grade phosphate mineralisation (pyroxenite zone).

As such Complex I hosts both Niobium and Phosphate economically significant mineralisation.

Chapadão – Phosphate
Weathering processes generated a thick weathering cover that, on average, is 150m thick which typically contains the horizontal tabular mineralised zones which are very extensive. During the weathering process some layers were silicified due to the water table variation, resulting in hard material within the mineralised zone. Mineralisation typically occurs as Apatite with the content varying based on the weathering profile which are outlined below:
- Red and yellow laterites, the base of this unit is enriched in magnetite; therefore rich in Fe2O3, which is the main component of the soil. This layer contains no mineralisation.
- Oxide level has the highest degree of alteration and its texture ranges from sandy to argillaceous, depending on the quantity of apatite and magnetite.
- Silexite can be found in the contact between the phlogopite zone and the vermiculite zone, or between the oxide mineralisation and the vermiculite zone. It can be found as vertical or horizontal deposits. It normally contains high grades of P2O5, but also high grades of Fe2O3;
- Vermiculite zone is found on top of the phlogopite zone and is represented by interstratified minerals, rhythmic layers of phlogopite and vermiculite,
- Phlogopite zone: the mica is fresher than in the previous layers,
- Partial weathered layer contains mainly carbonates; primary structures are clearly seen and also boulders often occur.

All mining operations is conducted by contractors via conventional truck and shovel open pit mining methods. Waste material from the pits is delivered through a series of haul roads to onsite waste dumps for storage at each of the current operations.

The Chapadão pit final pit design is 1.9-km long, 1.7-km wide, and 90-m deep. All mining to date has taken place in the upper zone of lateritic and saprolitic soils, targeting the oxidized ore. During the site visit it was noted that no history of instability or wall failures had occurred since the beginning of its operations. RPM noted that mine personnel performs daily visual inspections, which are documented in a check list form and stored in hard copy format.

The phosphate operations consists of two floatation concentrators which combined have a throughput rate of 5.8 mtpa ROM. Feed for the plants is oxide material from the adjacent Chapadão pit.

Beneficiation: Ouvidor
The key beneficiation production processes are crushing, milling, and flotation.

The two concentrators share a common crushing and crushed-ore stockpiling and reclaiming facility. The oreprocessing systems of both concentrators are identical, including two-stage grinding using rod mills as the first grinding stage. Rod milling is followed by low-intensity magnetic separation with rejection of the magnetic fraction and ball milling of the non-magnetic fraction.

The phosphate operations consists of two floatation concentrators which combined have a throughput rate of 5.8 mtpa ROM. Feed for the plants is oxide material from the adjacent Chapadão pit. The concentrators, produce a slurry concentrate which is pumped via a 7 km pipeline to the separating station within the Catalão Fertilizer plant. This station separates the fines and coarse materials within the slurry, all fines and 45% of the coarse material are fed directly to the Catalão Fertilizer Plant, the remaining 55% coarse material is transported 750km via rail to the Cubatão Fertilizer Plant.

Beneficiation: Ouvidor
The key beneficiation production processes are crushing, milling, and flotation. The beneficiation process increases P2O5 grade in the ore from 13% to 37%. The resulting phosphate concentrate is shipped to the Catalão processing plant. The process also yields barite as a by-product. The niobium tailings are supplied to the Tailings Plant for processing by the ........