# Relationship history for MSHA mine 3303483

Current hierarchy: **Fairmount Santrol → Best Silica Corp → Best Silica Company**

- 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:** Silica Sand & Gravel Inc → Best Silica Company; 1950-01-01 to 1980-12-04; source msha-controller-operator-history
- **controller_controls_mine:** Keesling Leroy → Best Silica Company; 1950-01-01 to 1980-12-04; source msha-controller-operator-history
- **controller_controls_operator:** Keesling Leroy → Silica Sand & Gravel Inc; 1950-01-01 to 1980-12-04; source msha-controller-operator-history
- **operator_operates_mine:** Set Silica Sand Inc → Best Silica Company; 1980-12-05 to 1984-03-31; source msha-controller-operator-history
- **controller_controls_mine:** Set Products Inc → Best Silica Company; 1980-12-05 to 1984-03-31; source msha-controller-operator-history
- **controller_controls_operator:** Set Products Inc → Set Silica Sand Inc; 1980-12-05 to 1984-03-31; source msha-controller-operator-history
- **operator_operates_mine:** Best Silica Corp → Best Silica Company; 1984-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Fairmount Santrol → Best Silica Company; 1984-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Fairmount Santrol → Best Silica Corp; 1984-04-01 to current/open; source msha-controller-operator-history