Gallium does not exist free in nature and to date (July 2022) there are only 9 mineral species for which it is an essential constituent
Hardness: 1.5 mohs
Colour: Silvery blue
Melting point: 29.76oC
Boiling point: 2200oC
Abundance in the Earth's crust: 19 parts per million by mass, 5.5 parts per million by moles (ChC).
Abundance in the Solar System: 40 parts per billion by mass, 0.6 parts per billion by moles (ChC).
In compounds gallium is in the oxidation state +3, as Ga3+.
It has the second largest liquid range of any element and is one of the few metals that is liquid near room temperature, melting in the hand. It also has the unusual property that (like water) it expands as it freezes (ChC).
The known gallium-bearing minerals are:
Krieselite is considered as a gallium-bearing mineral because, although the IMA formula does not include Ga, generally Ga substitutes for some Al
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