# Relationship history for MSHA mine 2400077

Current hierarchy: **Rhone-Poulenc S A → Rhone Poulenc North American Chemicals → Maiden Rock Silica 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:** Stauffer Chemical Company → Maiden Rock Silica Quarry; 1950-01-01 to 1987-11-30; source msha-controller-operator-history
- **controller_controls_mine:** Unilever United States Inc → Maiden Rock Silica Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Unilever United States Inc → Stauffer Chemical Company; 1950-01-01 to 1987-11-30; source msha-controller-operator-history
- **operator_operates_mine:** Rhone Poulenc North American Chemicals → Maiden Rock Silica Quarry; 1987-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rhone-Poulenc S A → Maiden Rock Silica Quarry; 1987-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rhone-Poulenc S A → Rhone Poulenc North American Chemicals; 1987-12-01 to current/open; source msha-controller-operator-history