Mineral Reserves

the quantity of mineral raw materials in the earth’s interior, on its surface, at the bottoms of water basins, and in surface and subterranean waters, as determined from information provided by geological explorations. This information makes it possible to calculate the size of bodies of minerals and by multiplying size by density to determine the weight of mineral reserves. In calculating re-serves of liquid and gaseous minerals (oil, underground waters, fuel gas), in addition to the volumetric method, a method of computing reserves by inflows into boreholes is also employed. For certain deposits of minerals, moreover, the quantity of the reserves of valuable components that they contain is calculated, for example, reserves of metals in ores. Mineral reserves in the earth’s interior are measured in cu m (building materials, fuel gases), in tons (oil, coal, ore), in kg (precious metals), and in carats (diamonds).

Calculations of the size of mineral reserves are of varying reliability, depending on the complexity of the geological structure of the deposits and on how detailed the geological exploration has been. Mineral reserves are divided into categories according to the degree of certainty of their de-termination. The system of classification of mineral reserves that is used in the USSR divides them into four categories: A, B, C₁, and C₂. Category A consists of mineral reserves explored in detail, with precisely defined boundaries of mineral bodies and their shapes and structure permitting the identification of natural types and industrial varieties of mineral raw materials in the interior of the deposit, as well as of the geological factors determining the conditions of their extraction. Category B includes mineral reserves that have been explored in a preliminary manner, with approximately determined contours of mineral bodies but without precise representation of the spatial position of natural types of mineral raw materials. Category C, includes reserves of explored deposits with complex geological structures, as well as little explored mineral reserves in new areas or in areas adjoining deposits that have been explored in detail; such reserves are estimated by extrapolation from geological information on deposits that have been surveyed in detail. Category C₂ consists of potential reserves that have been identified beyond the bounds of explored deposits by interpreting their geological structures and comparing them to similar mineral bodies that have been surveyed in detail.

Of the classifications of mineral reserves used abroad, the American classification is the most commonly used. In this classification there are three categories of reserves: (1) measured reserves, determined on the basis of measurements obtained from mining excavations and boreholes, (2) indicated reserves, estimated by extending the data of mining operations and drilling beyond the immediate area of these operations, and (3) inferred reserves, evaluated on the basis of general geological data.

Under the regulations existing in the Soviet Union, mineral deposits may be exploited if they contain a specified ratio of mineral reserves of the various categories. Three groups of deposits, with varying ratios of the categories of minerals, may be identified in terms of the complexity of their geological structure. The first group consists of mineral deposits of simple geological structure with a uniform distribution of valuable components. For this group not less than 30 percent of its reserves must have been explored to the extent of categories A and B, including not less than 10 percent to the extent of category A. The second group consists of deposits with a complex geological structure (not less that 20 percent of its reserves must have been explored to the extent of category B). The third group includes deposits with a very complex geological structure and an exceptionally uneven content of valuable components. The planning of mining enterprises and the allocation of capital investments for their construction or reconstruction is permitted if there are re-serves from category C₁.

In terms of their suitability for use in the national economy, mineral reserves are classified as “commercial” and “noncommercial.” Commercial mineral reserves are those that are feasible for development at the present level of technology and economics. Noncommercial mineral reserves are those that are not presently used because of their small quantity, low quality, or complex conditions of exploitation or processing; they may, however, in the future become an object of industrial development. In order to determine the indicators of commercial mineral reserves specific computations are made describing the industrial requirements of mineral raw materials, for example, the minimal thickness of mineral bodies, the minimal industrial content of valuable components in minerals, and the maximum permissible inclusions of rocks. When a mineral deposit gradually merges with surrounding rocks, the so-called bort content is esti-mated, that is, the content of a valuable component along which a boundary is drawn between the body of the mineral and the surrounding rocks. In the USSR the State Committee for Mineral Reserves in the USSR approves the requirements for estimating reserves, verifies the accuracy of reserve esti-mates, divides reserves into commercial and noncommercial groups, confirms reserves, and determines whether or not deposits are ready for industrial development by categories.