Caliche

SQM's Specialty Plant Nutrition, represented by Ultrasol™ and Qrop™ brands, is mostly based on natural caliche extraction.

The north of Chile has the biggest caliche mineral deposits known in the world and the only source of commercially-exploited natural nitrates in the planet.

Their geological origin is not clear. Caliche formation is believed to be the result of sediment deposits of an ancient interior sea or the accumulation of minerals resulting from erosion of Los Andes west face.

Caliche is under a 0.5 to 2.5 meter thick overload material layer, in mineral strata of 0.2 to 5 meters of power. Mineral concentrations in caliche vary from mine to mine. SQM annually exploits 30 million tons of caliche in aggregate.

Nitrates Process

Caliche overload is removed using bulldozers. Then, explosives are used to break the mineral, which is installed in trucks with front loaders. In Pedro de Valdivia, trucks haul and accrue mineral on piles or stocks near temporary railroad stations, where it is loaded on wagons bound to the production plant. In María Elena, trucks unload the mineral on a mobile primary crusher located at the area of the mine, after which it is taken by conveyor belts to the plant.

In both plants, caliche is ground mechanically until reaching a size of about ½ inch. Ground mineral is then transferred to a batch leaching plant, where its nitrate, iodine, and sulphate contents are extracted.

Mineral is leached in piles at Pampa Blanca mine, located in Sierra Gorda, obtaining solutions destined to iodine production. Subsequently, they are taken to solar evaporation ponds, where salts are crystallised using high nitrate concentrations transported by truck to Coya Sur plants, where they are used as a supply in potassium nitrate production.

Salar Brines
Brines, present in liquid basins located under the surface of the salar, are extracted thanks to strategically located pumping wells. After being extracted, they are pumped to evaporation ponds through which concentrated brines and salts are obtained.

Part of the pumped brine is recovered after a series of evaporations, in the form of a concentrated solution, by-product of potassium chloride. It is transported and processed for the obtention of lithium carbonate and boric acid in a plant located in the Salar del Carmen, near Antofagasta. Another part of brines already concentrated is reinjected to underground deposits of the salar.

Salts deposited in evaporation ponds are duly harvested and transported. Through grinding, floating, drying and prilling processes, potassium chloride and potassium sulphate are obtained.

Lithium process

The production of lithium carbonate is based on lithium chloride solutions obtained in the Salar de Atacama as a by-product of the production of potassium chloride. These solutions are then processed to produce lithium carbonate in a plant located in the Salar del Carmen, near Antofagasta. The brines that are not used are re-injected into the salt flats.
The Salar de Atacama contains one of the largest and best quality reserves of lithium-brine in the world. This is because the nucleus of the Salar is a saline body with brine deposits generated by water filtered through the sub-soil of the Andes mountain range. The brine of the Salar de Atacama possesses great, and sustainable, competitive advantages on a world scale, because it has higher concentrations of potassium, lithium and boron than other natural brine deposits.

Iodine and Iodine Derivatives

The solutions resulting from the leaching of caliche ore at the Pedro de Valdivia, María Elena, Nueva Victoria and Pampa Blanca facilities, are used to produce iodine. As in the case of nitrate and sulfate production, the process - that occurs in the plants of Pedro de Valdivia and Nueva Victoria - is well established. However, variations in the iodine and other chemical contents of the treated ore, as well as other operational parameters, require a high level of know-how to manage the process efficiently.


The solutions from the leaching of caliche will transform iodine to iodate form. Part of the iodate in the solution is reduced to iodide using sulfur dioxide, which is produced by burning the sulfur. The resulting iodide is combined with the rest of untreated iodate solution to release elemental iodine. The solid iodine is then refined through a smelting process and flaked or prilled. SQM has obtained patents in Chile and in the United States for its iodine prilling process.