Iodine

Symbol: I
Iodine is a halogen and a non-metal; it does not occur in its native state and so is not a valid mineral, although it can be produced in the laboratory.
Specific gravity: 4.93
Colour: Bluish black solid, purple vapour
Melting point: 113.5^oC
Boiling point: 184^oC
Abundance in the Earth's crust: 450 parts per billion by mass, 73 parts per billion by moles (ChC).
In nature, iodine occurs in the form of iodide ions, mainly in seawater. It is introduced into the food chain via seaweed and other sea-plants. It is also found in some minerals and soils (ChC).

Iodine-bearing minerals include:

Sulphides
demicheleite-(I)
grechishchevite
radtkeite

Iodides
coccinite
iodargyrite
marshite
miersite
moschelite

Iodates
brüggenite
dietzeite
lautarite
pohlite
schwartzembergite
seeligerite


Sulphides - the sulphide anion is S^2-
Iodides - the iodide anion is I^-
Iodates - the iodate anion is (IO₃)^-

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