In 1625 the Gamero brothers from Pampacolca, in the upper part of the Majes Valley, discovered rich veins of silver in Caylloma. The mines were called Santa Sata, San Cristóbal and Vicunas. On another hill, called the Apostoles, the mine of San Judas Tadeo. Later, still others were found, which allowed the establishment of 22 "trapiches" (mill for grinding mineral ore) in all. In 1631 Cajas Reales were set up with an ore foundry which functioned until 1781, at which time ore was sent to the foundry in the city of Arequipa.
These events produced profound changes in the Colca. Originally an agricultural valley of importance, as the presence of Gonzalo Pizarro, the brother of Francisco Pizarro, to whom the control and organization of the Collaguas region was entrusted, shows, it became a rich mining region which absorbed all available manpower. Workers were recruited by the "mita" system, or forced mining service.
Due to an abundant supply of manpower, indispensible for exploitation of the mines, the Colca became a strategic center during colonial times. Two other factors contributed: abundant food production and the presence of the llama herds. These animals were essential for transporting the mineral to ports such as Quilca, Arantas or Islay, and also for guaranteeing the supply of mercury, indispensible in the production of silver, which came from Huancavelica or was imported from Yugoslavia or Spain. The viceroy Conde Chinchón considered Caylloma as the ore deposit third in importance after Potosí and Huancavelica.
Thus new villages supplanted in importance those already established in the agricultural zone, such as Yanque, Lari and Chivay. Boom times arrived for some, especially Caylloma, Tisco and Callalli. Agricultural production fell dramatically, terraces were abandoned, there was famine and malnutrition, epidemics and death. The population was drastically reduced, as can be seen by a report by the viceroy of Toledo in 1570 which puts the population at 33,900 inhabitants. By the end of the 18th century it had fallen to 13,905.
The mining "mitas" did not only alter the relationship of servitude which the Collaguas had with Arequipa, but that with other communities such as Potosí and Huancavelica as well.
In the 18th century mining suffered a serious crisis. The scarcity of manpower, due to the fall in the population level, the difficulty in obtaining mercury due to the low production at Huancavelica, problems deriving from the war between England and Spain, and internal rebellions like that of Tupac Amaru, made it impossible to continue the exploitation of the mines. They were abandoned, or neglected, and fell into disuse. With the building of the Arequipa-Puno railroad, which allows better communication with Caylloma from Sumbay, mining activity was recommenced in this century, but without great effect on the Colca which remained forgotten.
There are other important mines in the area of the Colca besides those at Caylloma, namely Arcata and Orcopampa which is at the head of the Andagua Valley. They also were worked in Colonial times and continue to be exploited up to the present day.
There were also small mines in the Colca Valley itself, as is shown by the remains of a significant "trapiche" or ore mill a few kilometers from Chivay. In the decade of the 50's the mine called Madrigal, down water from Chivay, was opened and has a certain importance in the economy of the valley.