Re-evaluating ‘Bell Pits’: Evidence for Industrial Mineral Extraction from Circular Extraction Shafts / Shallow Shafts in the Pennine Lower Coal Measures from sites in North West Leicestershire and South Derbyshire

The term bell pit is frequently applied to small, circular excavation features encountered within Coal Measures strata; however, its appropriateness is debated where classic bell-shaped morphology and spoil mounds are absent. Mining historians increasingly favour the terms shallow shafts or circular extraction shafts in such contexts, particularly where the target mineral is uncertain. This paper presents a detailed case study from Blackfordby, North West Leicestershire, where over 300 unrecorded shallow shafts were identified during pre-development ground investigation and archaeological works.

The site lies within the Pennine Lower Coal Measures, where coal seams are thin and variable and historically associated with exploitation of industrial minerals including fireclay, pot clay and ironstone. A full site strip revealed a dense, grid-like arrangement of circular shafts up to 5 m deep, backfilled with loose mudstone gravel which were frequently water-bearing. The shafts did not exhibit classic bell pit profiles and failed to terminate within coal seams. Archaeological artefacts recovered from site date the activity to the 19 ^th century and suggest a potential link to local ceramic and brickmaking industries.

Comparison with a nearby site at Hartshorne demonstrates similar shallow shaft morphology, colour differentiation and lack of identifiable coal extraction, supporting interpretation as exploratory or evaluative excavations for industrial minerals rather than coal. The findings highlight the limitations of coal-centric models for interpreting shallow mining features within the Lower Coal Measures and emphasise the importance of integrating geological, archaeological and geotechnical evidence. From a development perspective, the case study illustrates the significant ground risk posed by such features and demonstrates how bulk excavation and re-engineering can provide a cost-effective, low-risk remediation strategy while avoiding long-term mining legacy constraints.