# Relationship history for MSHA mine 0401966

Current hierarchy: **Martin Marietta Materials Inc → Calaveras Materials Inc → Blackstone 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Stewart & Nuss Inc → Blackstone Pit & Mill; 1950-01-01 to 1988-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Monolith Portland Cement Company → Blackstone Pit & Mill; 1950-01-01 to 1988-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Monolith Portland Cement Company → Stewart & Nuss Inc; 1950-01-01 to 1988-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Cimenteries Cbr Cementbedrijven → Blackstone Pit & Mill; 1980-04-07 to 1999-05-26; source msha-controller-operator-history
- **operator_operates_mine:** Calaveras Materials Inc → Blackstone Pit & Mill; 1989-01-01 to 1999-05-11; source msha-controller-operator-history
- **controller_controls_operator:** Cimenteries Cbr Cementbedrijven → Calaveras Materials Inc; 1989-01-01 to 1999-05-11; source msha-controller-operator-history
- **operator_operates_mine:** Calaveras Materials Inc → Blackstone Pit & Mill; 1999-05-12 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Blackstone Pit & Mill; 1999-05-12 to 2021-09-30; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Calaveras Materials Inc; 1999-05-12 to 2021-09-30; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → Blackstone Pit & Mill; 2021-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Calaveras Materials Inc; 2021-10-01 to current/open; source msha-controller-operator-history