partial foreign ownership. Insofar as the mining and metallurgical industry is concerned, Mexicanization basic-ally means that Mexican interests must control the industry, not only as to the capital in-vestment required in the form of equity, but also that management of the business must be vested in Mexican hands. Furthermore, management and technical assistance contracts that permit mining and metallurgical operations to be directed by foreign interests are frowned upon by the government. They are subject to strict supervision if they wish to obtain the tax benefits that are granted to the mining industry under the present law. The Mexicanization law states that a mining concession has a life of 25 years from the date of issuance, but can be renewed for an indefinite period of time provided (1) that the title holder has fulfilled all the requirements established by law to avoid its forfeiture and (2) that the concession is held by a Mexican national or a Mexicanized corporation. Under this law, all concessions issued prior to the law of 1961 must be Mexicanized. It also provides that an individual or legal entity cannot hold, either through concession or a lease, more than a given acreage for mining purposes that is, from 1,000 to 10,000 hec-tares, with the size depending on the ore or ores to be mined and covered by the respective concession. The final acreage can be three times the size of the area covered during the exploration period, which consists of the first five years of the life of the concession. Applications for mining concessions are filed with the relevant Mining Agency, of which there are 37 at present. In applying for a concession, a company must state its name, business location, official registered name in the Mining Registry, and the name of its Mexican representative, together with the name, description, survey, and map (or maps) of the various mining claims or concessions or both. Types of Concessions There are four types of concessions ordinary mining concessions, national mining reserves, special concessions, and beneficiation plants. Ordinary Mining Concessions Ordinary mining concessions are granted exclusively to Mexican nationals or to companies in which Mexican nationals own not less than 51 percent of the capital. Each concession covers a single claim with a maximum surface of 500 hectares and permits the exploitation of a maximum of eight mineral substances. Individuals and companies are limited to claiming 4,000 hectares for the extraction of gold, silver, lead, copper, zinc, fluoride, iron, titanium, or similar metals and 1,000 hectares for mercury, tungsten, molybdenum, and any other substances not enumerated. Ordinary mining concessions have a life of 25 years. (The mineral rights and obligations of concession holders are covered in detail in the mining code.) National Mining Reserves The Ministry of National Patrimony has authority to establish national mining reserves over any substances or mining areas, including all placer deposits. When such reserves are established, no concessions are permitted for any of the reserved elements or areas. Sub-stances that are considered to be essential to the industrial development of the country may also be held as national reserves. Minerals included in the national reserves at present are iron ore, coal, sulfur, uranium, thorium, and all placer minerals. Table 6 summarizes the minerals and areas that are currently considered to be national mining reserves. 18