Bauxite on the Konkan coast sits near the surface, beneath a few metres of soil and laterite. Ore that shallow is not reached by shafts and tunnels. It is mined open-cast: from the surface down, in a series of horizontal steps called benches.
Why open-cast suits lateritic bauxite
Lateritic bauxite forms as a blanket across plateau tops, typically within the first couple of tens of metres. That geometry has three consequences.
- Low overburden. Only topsoil and the laterite cap need to be removed to reach ore, so the stripping ratio is modest.
- Flat, wide ore bodies. Benches can follow the ore horizontally across the deposit.
- Soft to moderately hard ground. Much of the profile can be dug by hydraulic excavators; where the cap is hard, it may be ripped or broken by controlled blasting under the applicable regulations.
The bench, explained
A bench is a level working platform with a near-vertical face. A pit is a staircase of benches, each one a few metres high.
- Bench height is kept within the safe reach of the excavator working it.
- Bench width leaves room for machines to work and for haul trucks to pass.
- Face slope and the overall pit slope are designed to keep the walls stable, including through the monsoon.
India's metalliferous mines regulations, enforced by the Directorate General of Mines Safety, set requirements for benching, slopes and safe working. We cover safety in zero harm: mine safety and DGMS norms.
A bench, step by step
- Survey and mark out the block to be mined from the deposit model built during exploration and drilling.
- Strip and bank the topsoil, storing it separately so it can be returned during reclamation.
- Remove the laterite cap and other overburden, placing it where it can later backfill worked-out areas.
- Excavate the ore bench by bench, keeping the floor above the clay-rich lithomarge to avoid diluting the ore with silica.
- Haul to the stockpile by truck, where ore is sampled before processing.
- Backfill and restore each worked-out bench as mining moves on.
Grade control at the face
Open-cast mining is not just about moving tonnes; it is about moving the right tonnes. Grade control at the face, using the drill model and fresh samples, lets the mine send higher-alumina ore to one stockpile and other material elsewhere. That is what makes it possible to supply several bauxite grades from one deposit.
Working with the monsoon
The Konkan monsoon brings very heavy rain from roughly June to September. Open pits must manage water: drainage channels around and within the pit, settling ponds to hold back sediment, stable haul roads, and stockpiles protected from washing out. Planning ahead lets ore be mined and stockpiled in the dry months so that supply continues through the wet season. Our post on dust and water management goes further.
What it looks like at Minequor
Minequor's 175-acre mine in Raigad uses systematic open-cast mining in benches. Topsoil is stripped and banked before excavation, and worked-out benches are progressively backfilled and restored. Ore then moves to on-site crushing, screening and grading. The full sequence is laid out on our operations page.