# Relationship history for MSHA mine 3600516

Current hierarchy: **Heidelberg Materials AG → Heidelberg Materials Northeast LLC → Curtin Gap Quarry**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Herbert R Imbt Inc → Curtin Gap Quarry; 1950-01-01 to 1986-11-12; source msha-controller-operator-history
- **controller_controls_mine:** Herbert R Imbt Inc → Curtin Gap Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Herbert R Imbt Inc → Herbert R Imbt Inc; 1950-01-01 to 1986-11-12; source msha-controller-operator-history
- **operator_operates_mine:** Herbert R Imbt Inc → Curtin Gap Quarry; 1986-11-13 to 1988-11-13; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Curtin Gap Quarry; 1986-11-13 to 1988-11-13; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Herbert R Imbt Inc; 1986-11-13 to 1988-11-13; source msha-controller-operator-history
- **operator_operates_mine:** Heidelberg Materials Northeast LLC → Curtin Gap Quarry; 1988-11-14 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hanson PLC → Curtin Gap Quarry; 1988-11-14 to 2007-08-22; source msha-controller-operator-history
- **controller_controls_operator:** Hanson PLC → Heidelberg Materials Northeast LLC; 1988-11-14 to 2007-08-22; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Curtin Gap Quarry; 2007-08-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Heidelberg Materials Northeast LLC; 2007-08-23 to current/open; source msha-controller-operator-history