A highly colloidal clay mineral, Bentonite derives its name from the place where its presence and usages were first discovered - Fort Benton, America. Its hydration, swelling, water absorption, and other properties make it a multi-application product for diverse industries, finding usage as a mud constituent for oil and water well drilling. GMDC’s Bentonite mines are located at Surkha North, Bharuch.

| Bhavnagar (Bentonite) | ||||
| Address | Post - Malpar, Ta - Bhavnagar, Dist. – Bhavnagar (Gujarat) - 364 002 | |||
| Name of the Mine | Surkha (North) Lignite Mine | |||
| Agent | Mr. B. K. Mahato | |||
| Contact No. | 9727792768 | |||
| Manager | Mr. S.K. Mathur | |||
| Contact No. | 9727792825 | |||
| Bentonite Quality Parameter (Chemical) |
Constitute | Received Base analysis | ||
| SiO2 (%) | 42 - 45 | |||
| AlO2 (%) | 25 - 30 | |||
| Fe2O3 (%) | 10 - 15 | |||
| TiO2 (%) | 2 - 4 | |||
| CaO (%) | 1 - 2 | |||
| Na2O (%) | 0.6 - 0.7 | |||
| K2O (%) | 0.05 - 0.1 | |||
| LOI (%) | 10 - 11 | |||
| Bentonite Quality Parameter (Physical Property) |
Constitute | Received Base analysis | ||
| Gel Value (%) | < 10 | |||
| Swellingin Index (ml) | < 10 | |||
| Liquid Limit (%) | 80 - 85 | |||
| pH Value | 7.5 - 8.5 | |||
| Moisture Content (%) | 4 - 6 | |||
| Oil Absorbent (ml / 100 gm) | 35 - 41 | |||
| Viscosity (centipoises) | 15 - 20 | |||
| Sector-wise Bentonite Users | Fertilizers | |||