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Costa Rica.

Central America

Costa Rica

MAINLY because of its political stability, Costa Rica has for many years been the most prosperous of the Central American republics, a position bolstered by high levels of aid from the U.S.A. Nevertheless, tight fiscal and monetary policies have had to be introduced by the government in the face of mounting trade imbalances and a substantial foreign debt, as well as an inflation rate of about 28%, a marked increase from the 10% level of 1989. GDP growth was around an estimated 3.8% in 1990, compared with 5.6% in the previous year.

Emphasis continues to be placed by the Costa Rican Government on the development of the country's gold and silver potential, associated with deposits occuring as fissure and stockwork quartz veins along faults and fracture zones in andesitic volcanics and also as stockwork quartz veins associated with rhyolites. Opportunities for foreign investment now seem even more favourable than before with the report in September 1990 that the Ministry of Mines was considering pulling out of gold exploration and development because of the high levels of government investment required.

An expansion programme by Ariel Resources Ltd, the largest underground gold producer in Costa Rica, has been carried out at its Esperanza mine, Guanacaste Province, to raise production from 3,000 oz/y to over 12,000 oz/y. The company has also reported that there is a block of 13,200 t of possible ore grading just over 9 g/t; another block contains 127,000 t of inferred ore of probably similar grade. Within the Tilaran-Aguacate gold province, surface sampling by Equinox Resources Ltd at its Macona open-pit mine has shown gold mineralization to extend over a distance of more than 7 km, with resources amounting to 2-3 Mt of potential sulphide ore. The mine, 65 km WNW of San Jose, is to have an output of some 5,000 oz/y gold. Proved reserves amount to about 5 Mt averaging 1.6 g/t gold, based on a cut-off grade of 0.5 g/t.

Other Canadian companies have been particularly active in Costa Rica in recent years in the search for, and development of, various gold prospects. The most prominent of the current projects is that associated with the Recio property in the Abangares gold district, where Greenstone Resources Ltd, Toronto, has delineated 16 gold-silver vein systems with a combined strike length of more than 9 km. Two prospective orebodies, namely, Recio Norte and the Verdun Norte, are to be worked by both openpit and underground methods. The former deposit is estimated to contain 725,000 t, of which 166,320 t are fully developed as open-pit reserves with an average grade of 0.09 oz/t of gold, and assuming an average cut-off grade of 0.03 and a stripping ratio of 2.5:1. Drilling is expected to raise this tonnage to 300,000 t. Beneath the open pit, drilling has also revealed a grade of 0.27 oz/t of gold over 1.5 m at a depth of 75 m. Underground reserves in the Verdun Norte zone of the Santa Ana deposit, situated nearly 600 m to the southeast of Recio Norte, are estimated at 180,510 t grading 0.237 oz/t of gold, but further drilling and drifting may similarly raise reserves to 300,000 t. Open-pit reserves on Santa Ana are 75,000 t with an average grade of 0.09 oz/t of gold. There are plans to produce about 21,000 oz/y of gold initially, assuming a grade of 0.19 oz/t and a 92% recovery.

Early in 1990, the Toronto-based Black Cliff Mines Ltd was granted an option to Lyon Lake Mines Ltd of Rouyn-Noranda to earn a 50% interest in four gold prospects. These include the Beta Vargas deposit which has been estimated by Minera Nacional SA (Minasa), a government exploration agency, to contain 6.7 Mt averaging 1.17 g/t gold. Higher grade zones have been delineated. The Canamazo prospect contains an estimated 265,000 t grading 6.4 g/t gold. In late 1990, confirmatory drilling was being carried out as part of plans for a 3,000-5,000 t/d operation to start by the end of 1991. Similarly, Rio Chiquito Mining Co., a joint venture involving Mallon Resources Corp., Sunshine Mining Co. and Red Rock Ventures Inc. is to conduct mining operations at Rio Chiquito, in the Guanacaste Province. Sunshine has the option to earn a 50% interest and become manager of the venture after assessing all available data including a recently completed 4,000 m drilling programme.

Production of other minerals in Costa Rica continues to be very limited.

Much information has become available on the country's mineral resources through the completion, in 1990, of the first phase of Proyecto Anglo-Costarricense de Minerales Industriales, a bilateral Technical Co-operation Project involving the Direccion de Geologia, Minas y Hidrocarburos and the British Geological Survey.

                  1987    1988    1989
Diatomite (t)    5,200   5,200   6,000
Gold (kg)          336     313     387
Salt (t)        12,650    n.a.    n.a.

n.a. = not available.

A. Notholt, Mineral Resource Consultant, London, U.K.
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Title Annotation:review of the Costa Rican mineral mining industry in 1990
Author:Notholt, A.
Publication:Mining Magazine
Article Type:Brief Article
Date:Jan 1, 1991
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