# Relationship history for MSHA mine 0900993

Current hierarchy: **Robbie M  Worley → T & C Quarries Inc → Sapphire Blue 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

- **controller_controls_mine:** Robbie M  Worley → Sapphire Blue Quarry; 1980-09-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** T & C Quarries Inc → Sapphire Blue Quarry; 1987-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robbie M  Worley → T & C Quarries Inc; 1987-01-01 to current/open; source msha-controller-operator-history