Depreciation of assets is determined using the straight-line method over the estimated useful lives of such assets as follows:
| Years | |
| Buildings and other constructions: | |
| Administrative facilities | Between 35 and 48 |
| Main production structures | Between 30 and 49 |
| Minor production structures | Between 20 and 35 |
| Machinery and equipment: | |
| Mills and horizontal furnaces | Between 42 and 49 |
| Vertical furnaces, crushers and grinders | Between 23 and 36 |
| Electricity facilities and other minors | Between 12 and 35 |
| Furniture and fixtures | 10 |
| Transportation units: | |
| Heavy units | Between 11 and 21 |
| Light units | Between 8 and 11 |
| Computer equipment | 4 |
| Tools | Between 5 and 10 |