# Relationship history for MSHA mine 5001230

Current hierarchy: **Rio Tinto Group → United States Borax & Chemical Corp → Quartz Hill Project**

- 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:** United States Borax & Chemical Corp → Quartz Hill Project; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Rio Tinto Group → Quartz Hill Project; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Rio Tinto Group → United States Borax & Chemical Corp; 1950-01-01 to current/open; source msha-controller-operator-history