Mining

Survey and Demarcation

Two kinds of deposits may be distinguished in Cuamba: the "alluvial" and "in situ" deposits. The initial prospecting is done under the guidance of our geologist. An arc of garnetiferous biotite schist traverses the mining area.

Mechanized Mining

The alluvial deposits lend themselves readily to mechanization. The deposits are marked in a numbered grid pattern, enabling the identification of richer deposits from visual inspections and results from washing plant recovery. The day-to-day direction of mining is controlled by a pit supervisor. There is constant feedback from the washing plant to the mining area to identify high-quality material.

After removing the overburden, garnet-bearing alluvium is loaded onto dumper trucks and driven to the washing plant for recovery.

Recovery

The recovery process consists of two sections: the washing plant and the sorting office.

Washing Plant

The washing plant has a hopper to receive the alluvial material, which is led into the scrubber and trommel to separate sand and clay from the coarse material among which are the garnets. The jigs separate the garnets from other coarse material.

Assorting and Quality Control

The garnets are shifted to the quality control section. All garnets, starting from 0.5 grams, are checked for type and quality, each by hand using three different selection methods. They are inspected with the naked eye using ordinary light tables (eye-clean quality) and bedside lamps (lamp-clean quality), and with the use of glass fiber and magnifiers for more detailed inspection and selection of fiber-clean quality. As a result, the exported gems reach a rejection rate of a maximum of 5%.