The Charm City Experience

 In the 16th century, mercury amalgamation methods were brought to the Americas by Spanish colonizers (1,2). Gold mining in the Portovelo-Zaruma region of Ecuador began in the 1550’s when indigenous populations and African slaves worked small excavations (3). The Zaruma Gold Mining Limited Company was founded in 1880 and by 1897 was bought by SADCO, an American company which possessed one of Ecuador’s only large-scale mines between 1897-1950 and extracted more than 1000 tons of gold (4,5). After SADCO, CIMA, a local state owned company, occupied the mine in Southern Ecuador and extracted 11 tons of gold before going bankrupt in 1978 (6). CIMA’s bankruptcy caused many miners to become unemployed and some to informally return to the abandoned mine site, leading to the emergence of small-scale mining (7,8). 

By the 1980’s two other mining districts developed in Southern Ecuador, organized by cooperatives and driven by a rise in gold prices. Just like in Zaruma, these mining districts also materialized in response to abandoned large-scale mining operations (7). In the 1990’s technological advances to extract, transport, mill, and process ore arose (6,7,9). New technologies like cyanidation, chilean mills, and chanchas existed alongside older methods like gravity concentration, and amalgamation (7). Processing center owners took advantage of informal miners and created business surrounding custom milling to crush, grind, and concentrate ore (6).

By as recent as 10  years ago, the industry became dominated by mercury amalgamation (10). Today, in Portovelo-Zaruma, almost all chilean mill processing centers include cyanidation at some step in the gold extraction process in addition to mercury amalgamation. ln the Puyango River basin, 110 small riverside plants process ore from over 400 mines. This ore is processed using a mixture of mercury amalgamation and cyanide leaching which results in the extraction of 9-10 tons of gold annually (8).

 References