# Relationship history for MSHA mine 0201136

Current hierarchy: **Imerys S A → Imerys Perlite USA, Inc → Superior Pit & 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:** Harborlite Corp → Superior Pit & Mill; 1978-03-09 to 1992-11-15; source msha-controller-operator-history
- **controller_controls_mine:** William G  Blunt → Superior Pit & Mill; 1978-03-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** William G  Blunt → Harborlite Corp; 1978-03-09 to 1992-11-15; source msha-controller-operator-history
- **operator_operates_mine:** Imerys Perlite USA, Inc → Superior Pit & Mill; 1992-11-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Alleghany Corp → Superior Pit & Mill; 1992-11-16 to 2005-07-14; source msha-controller-operator-history
- **controller_controls_operator:** Alleghany Corp → Imerys Perlite USA, Inc; 1992-11-16 to 2005-07-14; source msha-controller-operator-history
- **controller_controls_mine:** Imerys S A → Superior Pit & Mill; 2005-07-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Imerys S A → Imerys Perlite USA, Inc; 2005-07-15 to current/open; source msha-controller-operator-history