# Relationship history for MSHA mine 4104521

Current hierarchy: **Grayson County Sand and Gravel → Wildcatter Sand Services, LLC → Grayson County Sand & Gravel**

- 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:** Stringfellow Sand Pit → Grayson County Sand & Gravel; 2005-02-18 to 2009-11-29; source msha-controller-operator-history
- **controller_controls_mine:** Joel Thomas  Stringfellow → Grayson County Sand & Gravel; 2005-02-18 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Joel Thomas  Stringfellow → Stringfellow Sand Pit; 2005-02-18 to 2009-11-29; source msha-controller-operator-history
- **operator_operates_mine:** North Texas Sand Farm Inc → Grayson County Sand & Gravel; 2009-11-30 to 2020-10-31; source msha-controller-operator-history
- **controller_controls_mine:** Layne  Edwards → Grayson County Sand & Gravel; 2009-11-30 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Layne  Edwards → North Texas Sand Farm Inc; 2009-11-30 to 2020-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Wildcatter Sand Services, LLC → Grayson County Sand & Gravel; 2020-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Joelray  Stringfellow et al → Grayson County Sand & Gravel; 2020-11-01 to 2023-12-11; source msha-controller-operator-history
- **controller_controls_operator:** Joelray  Stringfellow et al → Wildcatter Sand Services, LLC; 2020-11-01 to 2023-12-11; source msha-controller-operator-history
- **controller_controls_operator:** Scott  Sherman et al → Wildcatter Sand Services, LLC; 2020-11-01 to 2023-12-11; source msha-controller-operator-history
- **controller_controls_mine:** Grayson County Sand and Gravel et al → Grayson County Sand & Gravel; 2023-12-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Grayson County Sand and Gravel et al → Wildcatter Sand Services, LLC; 2023-12-12 to current/open; source msha-controller-operator-history