# Relationship history for MSHA mine 0900042

Current hierarchy: **Polycor Inc → Polycor Georgia Granite Quarries Inc. → Keystone Blue 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

- **operator_operates_mine:** Keystone Granite Company → Keystone Blue Quarry; 1950-01-01 to 2024-03-04; source msha-controller-operator-history
- **controller_controls_mine:** George  Oglesby Jr → Keystone Blue Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** George  Oglesby Jr → Keystone Granite Company; 1950-01-01 to 2024-03-04; source msha-controller-operator-history
- **controller_controls_mine:** Polycor Inc → Keystone Blue Quarry; 2024-03-04 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Polycor Georgia Granite Quarries Inc. → Keystone Blue Quarry; 2024-03-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Polycor Inc → Polycor Georgia Granite Quarries Inc.; 2024-03-05 to current/open; source msha-controller-operator-history