On condensing the vapor, he produced dark lustrous crystals. This was in fact iodine. The name clearly refers to its unique color. It was originally prepared from the ashes of kelp and other seaweeds, just as Courtois had done. However at the present time, the major sources of iodine are natural and oil field brines, from which they are separated by a special process known as ion exchange chromatography.
Kelps are very rich in iodine.
I may tell you that although iodine in large amounts is poisonous to our body, it does need iodine in very small quantities. It is needed by the thyroid gland to make the hormone thyroxine. If someone's diet is deficient in iodine, his thyroid gland may enlarge. This disease is known as goitre. Kelps are so rich in iodine, that people who consume kelps don't suffer from goitre at all.