# Relationship history for MSHA mine 0800375

Current hierarchy: **Risinger H B → Seminole Fertilizer Corp → Ridgewood Mill**

- 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:** W R Grace & Company → Ridgewood Mill; 1950-01-01 to 1988-10-31; source msha-controller-operator-history
- **controller_controls_mine:** W R Grace & Company → Ridgewood Mill; 1950-01-01 to 2021-09-21; source msha-controller-operator-history
- **controller_controls_operator:** W R Grace & Company → W R Grace & Company; 1950-01-01 to 1988-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Seminole Fertilizer Corp → Ridgewood Mill; 1988-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Risinger H B → Ridgewood Mill; 1988-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Risinger H B → Seminole Fertilizer Corp; 1988-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Standard Industries Holdings Inc → Ridgewood Mill; 2021-09-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Standard Industries Holdings Inc → W R Grace & Company; 2021-09-22 to 1988-10-31; source msha-controller-operator-history