How is mining categorised in Bolivia?
In Bolivia, according to the Ministry of Mining and Metallurgy, different types of mining can be identified with the mining activity in the country classified into four (04) categories:
Next, we will briefly review each one:
a) State Mining: State
State Mining is represented by those mining operation whose ownership and administration belong to the COMIBOL and operate through Shared Risk Contracts, Leases and Services.
b) Medium Scale Mining
Medium Scale Mining is represented by the Association of Miners, who must meet certain production volume requirements, including production of more than 500 tons per day, as well as other particular investment and business organisation characteristics.
c) Small Scale Mining
Small Scale Mining is represented by mining operations that process less than 500 tons per day.
d) Mining Cooperatives
Mining cooperatives are small groups of between 50 and 80 workers who meet in cooperatives to take part in a concession granted by the State. Cooperatives have developed significantly over time, both in production volumes and in labour. Currently, there are about 510 mining cooperatives in Bolivia. It can be stated that cooperative mining is considered to be artisanal mining.
These mining cooperatives in turn are subdivided into three (03) large groups:
The "traditional" mining cooperatives exploit deposits of tin, tungsten, lead-silver-zinc compounds, antimony and bismuth. In most cases they work in old COMIBOL mines, and are made up of the same ex-workers of the state company. Sometimes on the same site (for example, Cerro Rico de Potosí, Siglo XX, Viloco, etc.), several large cooperatives work simultaneously meaning that several thousand miners can congregate (for example, from 6,000 to 8,000 cooperative members in the Cerro Rico de Potosí).
While some miners sell the mined ore, others perform their own concentration rustically using quimbaletes, champalavadores, maritales and buddles. A common environmental impact in traditional cooperatives is the emission of highly acidic waters carrying heavy metal ions, which find their way into the rivers. The responsibility for this impact is debatable, and it must be established whether it's the cooperatives or a legacy of COMIBOL. There is a considerable number of small businesses (small-scale mining) that work in traditional minerals. Its activities are focused on antimony mines (partially with gold), compounds (lead-silver-zinc) and some in tin and tungsten. Generally, these companies work in a mechanised way, both in the explotation or extraction of the cargo and in the concentration, treating small tonnages (<50 t/day).
The operate in almost all the terretory of Bolivia, especially in the region of the eastern slope of the Andes and also in the lower part to the border with Brazil.
From the mining oint of view, they use full range of technical possibilities, from the pillory and shovel, to heavy equipment for the movement of large volumes of land.
For the transport of the gold material, they use metal bags or forklifts to loader shovels (front) and large dump trucks.
For the separation of gold from the gravel, they use gutters (laundries), for the retention of gold they use stones (tojlla) high metallic lugs. The thick gold of the pre-concentrates of the gutters is recovered directly with a tray and the fine content is amalgamated with mercury. The amalgamation is done manually or mechanically (in amalgamating drums or mixers similar to small concrete mixers).
This mining alters the landscape, by the destruction of terraces and fertile beaches, without any intention of restoration. "The capacity of these cooperatives in some cases reaches up to 1,000 m3/day, due to the total absence of a planned, orderly and systematic mining, large areas of originally fertile land are transformed into chaotic piles of stone, unusable for cultivation".
These cooperatives work in primary deposits (hard rock), which contain veins of auriferous quartz, usually accompanied by metal sulphides or oxides. The processing of gold is carried out in different ways. The most rustic is manual crushing, followed by grinding in stone mills (quimbaletes), which can be carried out dry or wet. Under the latter form, mercury is generally used combining grinding with amalgamation. The use of mercury in cooperative gold mining represents, without a doubt, one of the most serious environmental impacts. As a result of the intense crushing in the mills, most of the mercury is atomised forming what is known as "mercury flour" (spheres of 30 to 50 um in diameter), which does not serve to amalgamate. This forces the miners to use more mercury -up to 10 times the amount compared to the gold extracted. Because almost no mine has an appropiate tail deposition system, the mercury flour generated by the mills goes along the tails and into the rivers.