FMF - Friends of Minerals Forum, discussion and message board

[Tom Mazanec]

I am reading every mineral book I can get from the library, and I sometimes read native mercury as being present, and even counted as an "official" mineral.
Outside of Antarctica and maybe Greenland (which are not the localities given for it), how can this be? At Earth's normal temperature, mercury is a liquid, which would quickly evaporate. How can the drops of mercury I read of survive?

[Bob Harman]

There will be others that post, knowing much more than I, but MERCURY is both an element and a mineral, much like silver, gold, copper, iron, and several other elements/minerals. This is by convention as much as anything else.

The difference for mercury though is that its melting point is much lower than the other minerals/elements so it is a liquid at ambient temperatures, while the others are solids at ambient temperature . However, even being a liquid, it does not appreciably evaporate at ambient temperatures unlike water and most other liquids. I think evaporation has to do with vapor pressure. Mercury has a different vapor pressure than water and most other liquids, so it remains essentially untouched over long time periods as most other liquids slowly or rapidly evaporate. CHEERS.....BOB

[GneissWare]

Here is an example. This specimen was collected in the 1960s and is still covered with balls of liquid Mercury.

https://www.mineral-forum.com/message-board/viewtopic.php?p=20921#20921

[alfredo]

Stability and endurance are NOT requirements for being an "official" mineral. There are many unstable species that disappear soon after you collect them, for one reason or another. Mercury is relatively tough, compared to say ikaite or downeyite, or even melanterite.

Technically, liquids don't satisfy the criteria for being mineral species, according to IMA definitions (not universally accepted), but mercury has been unscientifically "grandfathered in", just out of historical tradition. Personally, I'd go further than that and accept any natural liquid of geological origin with a fixed chemical composition, so that would include liquid carbon dioxide (present as inclusions in some gemstones), liquid sulphur (which I've personally observed dripping out of volcanic fumaroles), and even water! Oh, I just remember... I have a bottle labelled "mineral water" in the kitchen. See - there's the proof! ;)) ...I think I'll go mix it with some whiskey now, and destroy the specimen by consumption.

[Pete Modreski]

And the native mercury occurs in mineralized bedrock below the surface, so it does not come in regular open contact with the atmosphere, to which it would indeed evaporate if given enough time. One probably would not expect to see any remaining liquid mercury in surface exposures of such rocks.

(I'm sure that someone must know, how long it would take a mercury droplet of a given size to evaporate, at given temperatures in the "room temperature" range and some stated conditions of air circulation. I have no idea what this time scale would be, but, I'm sure "someone" does.)

And mercury has always been considered a classic example of a "mineraloid", something that meets the other criteria to be a mineral species (definite composition, naturally occurring) but has no crystal structure, being liquid. Now, given that it belongs to this somewhat vaguely defined class of "mineraloids", whether it should still be counted as a "mineral" and appear in the lists of mineral species found somewhere--that is, I think, mostly a matter of semantics, you can treat this the one way, or the other. Most writers would list mercury along with the other minerals found at a locality. While still acknowledging that it is a mineraloid.