---
schema_version: "secwatch.filing_event.v1"
accession: "0001104659-25-003943"
form_type: "8-K"
ticker: "CNR"
cik: "0001710366"
company_name: "Core Natural Resources, Inc."
filed_at: "2025-01-16T23:59:59+00:00"
generated_at: "2026-05-28T00:09:23.068411+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Core Natural Resources seals Leer South longwall panel due to combustion; expects longwall resumption mid-2025

## Summary
- Temporarily sealing active longwall panel to extinguish isolated combustion-related activity.
- Expects to resume continuous miner development within 3 months and longwall mining mid-year.
- CEO says loss of around two quarters of longwall production at Leer South.
- Plans to apply water and nitrogen; re-entry multi-phased with ventilation controls.
- COO cites future mitigation steps in monitoring, degassing, and proactive systems.

## SEC filing metadata
- accession: 0001104659-25-003943
- form_type: 8-K
- ticker: CNR
- cik: 0001710366
- company_name: Core Natural Resources, Inc.
- filed_at: 2025-01-16T23:59:59+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1710366/000110465925003943/0001104659-25-003943-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1710366/000110465925003943/tm253501d1_8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001104659-25-003943
- JSON: https://secwatch.observer/filing/0001104659-25-003943.json
- Plain text: https://secwatch.observer/filing/0001104659-25-003943.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.