Iodine

A trace element recovered from Chilean nitrate deserts and Japanese gas brines, essential for X-ray contrast media, displays and human health.

Industrial minerals · No. 61

• Not on a critical list

The oceans hold about 90 billion tons of iodine, yet two-thirds of mined supply comes from one Chilean desert.

Chart: Illustration: Iodine

Where it comes from

Chart: Map of where it comes from

Iodine is never mined alone. It comes from Chile's Atacama caliche, heap-leached alongside nitrates, from brines pumped with gas in Japan, and from deep brines in Oklahoma.

Three things to know

1. Iodine's heavy atom absorbs X-rays, which is why it makes contrast media work, and X-ray contrast is its leading use worldwide.
2. Laminaria seaweeds concentrate iodine up to 0.45% of their dry weight, from seawater holding only 0.06 ppm.
3. By 2010 China declared iodine deficiency eliminated in all but its remotest provinces, largely through iodised salt.

The journey

1. 1 Ore or brineAtacama caliche or gas-field brines
2. 2 LeachingHeap leaching or brine extraction
3. 3 Blowing-outOxidised to crude iodine prill
4. 4 RefiningIodine crystal and compounds
5. 5 End usesContrast media, LCD film, drugs, feed

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