# Relationship history for MSHA mine 0405976

Current hierarchy: **Taiheiyo Cement Corp → CalPortland Cement Company → Gem Hill Mine Site**

- 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

- **controller_controls_mine:** Taiheiyo Cement Corp → Gem Hill Mine Site; 1990-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Cement Company → Gem Hill Mine Site; 2024-04-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → CalPortland Cement Company; 2024-04-25 to current/open; source msha-controller-operator-history