# Relationship history for MSHA mine 1800029

Current hierarchy: **Amrize Ltd → Amrize Mid-Atlantic Inc. → Amrize Rockville 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Rockville Crushed Stone Inc → Amrize Rockville Quarry; 1950-01-01 to 1987-12-10; source msha-controller-operator-history
- **controller_controls_mine:** C J Langenfelder & Son Inc → Amrize Rockville Quarry; 1950-01-01 to 1987-12-10; source msha-controller-operator-history
- **controller_controls_operator:** C J Langenfelder & Son Inc → Rockville Crushed Stone Inc; 1950-01-01 to 1987-12-10; source msha-controller-operator-history
- **controller_controls_mine:** Aggregate Industries PLC → Amrize Rockville Quarry; 1950-01-01 to 2009-04-29; source msha-controller-operator-history
- **operator_operates_mine:** Amrize Mid-Atlantic Inc. → Amrize Rockville Quarry; 1987-12-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Aggregate Industries PLC → Amrize Mid-Atlantic Inc.; 1987-12-11 to 2009-04-29; source msha-controller-operator-history
- **controller_controls_mine:** Holcim Ltd → Amrize Rockville Quarry; 2009-04-30 to 2015-07-09; source msha-controller-operator-history
- **controller_controls_operator:** Holcim Ltd → Amrize Mid-Atlantic Inc.; 2009-04-30 to 2015-07-09; source msha-controller-operator-history
- **controller_controls_mine:** Holcim Ltd → Amrize Rockville Quarry; 2015-07-10 to 2025-06-22; source msha-controller-operator-history
- **controller_controls_operator:** Holcim Ltd → Amrize Mid-Atlantic Inc.; 2015-07-10 to 2025-06-22; source msha-controller-operator-history
- **controller_controls_mine:** Amrize Ltd → Amrize Rockville Quarry; 2025-06-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Amrize Ltd → Amrize Mid-Atlantic Inc.; 2025-06-23 to current/open; source msha-controller-operator-history