# Relationship history for MSHA mine 0402304

Current hierarchy: **Rio Tinto Group → U S Silica Company → Oceanside Plant**

- 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:** Crystal Silica Company → Oceanside Plant; 1950-01-01 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Ottawa Silica Company → Oceanside Plant; 1950-01-01 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Ottawa Silica Company → Crystal Silica Company; 1950-01-01 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Rio Tinto Group → Oceanside Plant; 1986-04-02 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** U S Silica Company → Oceanside Plant; 1987-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rio Tinto Group → U S Silica Company; 1987-01-01 to current/open; source msha-controller-operator-history