jadding

Jadding is the practice of cutting a horizontal cavity or undercut into the lower face of a coal seam, ore body, or stone layer, working from the surface or from within an excavation. The undercut is driven inward beneath the overlying material, creating an overhang or void that destabilizes the strata above it. Once sufficient jadding is complete, the weakened overburden fractures and falls away under its own weight, allowing miners to extract the coal or stone below with reduced effort and safer working conditions than if they were to remove material from above downward.

The technique was especially common in coal mining where the lower coal seam, often softer than surrounding stone, could be undercut with hand tools or simple mechanical equipment. A miner would work horizontally or slightly upward with a pick or similar tool, advancing the undercut perhaps two to three meters (or more, depending on the seam thickness and stability). Once the roof became unstable, it would collapse inward, bringing down the stone and any intermediate material with it.

Variants and application

Jadding differs from simple undercutting in that it is a systematic, deliberate method rather than an incidental feature of extraction work. In stone quarrying, jadding allowed workers to drop large blocks without extensive drilling or blasting. In coal mines, it reduced the weight of material a miner had to handle manually and created safer extraction geometry. The method was labor-intensive but required minimal equipment, making it practical in mines with limited access to machinery.

The term itself is now archaic, having largely disappeared from active mining vocabulary by the mid-20th century as mechanical undercutting machines, hydraulic props, and controlled blasting techniques became standard practice. Modern mining terminology tends to use phrases like 'undercutting', 'slabbing', or specific machine names instead. Jadding survives mainly in historical mining records and older technical literature.

The practice was hazardous: a premature or uncontrolled collapse could trap workers or cause large volumes of stone to fall unpredictably. Proper assessment of roof stability and careful progression of the undercut were essential but difficult to judge by eye and experience alone.