ASSESSMENT OF ORE DILUTION AND QUALITY CONTROL PRACTICES IN UNDERGROUND MINING OPERATIONS

Abstract

Ore dilution and quality control represent two of the most critical challenges facing modern
underground mining operations, directly impacting economic viability, operational efficiency, and
resource recovery. Underground mining, particularly in high-grade deposits with complex
geometries, presents unique challenges for dilution control that differ significantly from open pit
operations. This capstone research examines the causes, measurement, and control of ore dilution
at Kinsenda Copper Mine, an underground operation located in the Haut-Katanga Province of the
Democratic Republic of the Congo, near the Zambian border. Kinsenda Mine, operated by
Kinsenda Copper Company SARL (a subsidiary of Metorex under Jinchuan Group International
Resources), is considered one of the world's highest-grade active underground copper mines, with
an average reserve grade of 5.8% copper. The mine commenced production in 2017 and achieved
commercial production in early 2018, with a nameplate ore processing capacity of 600,000 tonnes
per annum.
This research employs a mixed-methods approach combining quantitative analysis of production
data with qualitative assessment of operational practices. Primary data were collected through
structured questionnaires administered to 52 respondents across geology, mine planning,
production, and quality control departments, semi-structured interviews with 12 key informants
including department heads and senior engineers, and direct observation of underground mining
and grade control activities. Secondary data included production records, geological reports, stope
performance data, and reconciliation reports from 2018 to 2024.
The study identifies primary dilution sources including overbreak during development and stoping
(accounting for approximately 38% of total dilution), geological complexity and structural
variability (29%), poor stope design and sequencing (18%), and inadequate ground support and
backfill practices (15%). Analysis of production data reveals dilution rates ranging from 9.2% to
22.5% across different stope types and ore zones, with an average of 14.8% over the study period.
Reconciliation analysis shows a systematic negative variance between planned and actual grades
averaging 8.5%, indicating significant grade control challenges. The economic impact is
substantial, with estimated revenue losses of approximately US$ 6.5 million annually due to
dilution-related grade reductions and increased processing costs.
Key findings reveal that dilution at Kinsenda Mine is exacerbated by the complex sediment-hosted
stratabound mineralization geometry, where copper occurs predominantly as chalcocite, bornite
and chalcopyrite hosted in detrital conglomerates, sandstones and argillaceous siltstones of the
Lower Roan Group. The orebody consists of a number of vertically stacked, tabular mineralised
zones varying in width from 1 m to 20 m, dipping moderately at 25° to 30°, making ore-waste
discrimination particularly challenging. The research proposes an integrated quality control
framework encompassing advanced geological modelling, stope design optimization, real-time
grade control, blast movement monitoring, and multi-disciplinary dilution control forums. The
findings contribute to the broader understanding of dilution management in high-grade sediment
hosted copper deposits and offer practical recommendations for improving ore recovery and
economic performance at Kinsenda Mine and similar underground operations.

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