# Relationship history for MSHA mine 0102150

Current hierarchy: **Blue Circle Industries Plc → Blue Circle Inc → Roberta 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Martin Marietta Materials Inc → Roberta Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Cement → Roberta Quarry; 1979-01-01 to 1983-05-17; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Cement; 1979-01-01 to 1983-05-17; source msha-controller-operator-history
- **operator_operates_mine:** Blue Circle Inc → Roberta Quarry; 1983-05-18 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Blue Circle Industries Plc → Roberta Quarry; 1983-05-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Blue Circle Industries Plc → Blue Circle Inc; 1983-05-18 to current/open; source msha-controller-operator-history