The largest accumulations of naturally occurring sodium nitrate are found in
Chile and
Peru, where
nitrate salts are bound within mineral deposits called
caliche ore.
[4] Nitrates accumulate on land through marine-fog precipitation and sea-spray oxidation/desiccation followed by gravitational settling of airborne NaNO
3, KNO
3, NaCl, Na
2SO
4, and I, in the hot-dry desert atmosphere.
[5] El Niño/La Niña extreme aridity/torrential rain cycles favor nitrates accumulation through both aridity and water solution/remobilization/transportation onto slopes and into basins; capillary solution movement forms layers of nitrates; pure nitrate forms rare veins. For more than a century, the world supply of the compound was mined almost exclusively from the
Atacama desert in northern Chile until, at the turn of the 20th century, German chemists
Fritz Haber and
Carl Bosch developed a process for producing
ammonia from the atmosphere on an industrial scale (see
Haber process). With the onset of
World War I, Germany began converting ammonia from this process into a synthetic
Chilean saltpeter, which was as practical as the natural compound in production of
gunpowder and other munitions. By the 1940s, this conversion process resulted in a dramatic decline in demand for sodium nitrate procured from natural sources.
