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Name: Michael
Status: other
Grade: 12+
Location: SC
Country: USA
Date: N/A


Question:
Is carbon dioxide in it's frozen form(dry ice) a mineral? And if it's not is it because it lacks a crystalline structure?



Replies:
Michael,

I do not think it could be accurate to describe Dry Ice as a mineral as it fails to meet the definition.

Any of a class of substances occurring in nature, usually comprising inorganic substances, as quartz or feldspar, of definite chemical composition and usually of definite crystal structure, but sometimes also including rocks formed by these substances as well as certain natural products of organic origin, as asphalt or coal.

Dry Ice is solidified carbon dioxide, which does not occur in Nature - at least not in the Earth's crust. On Earth CO2 only occurs as a gas, mostly in the atmosphere but it is also expelled from volcanoes and occurs as inclusions in some rock forms, including pumice where it fills some of the vesicles (bubbles) in the rock.

Now if you were to allow your definition to include planets outside Earth (where does Nature extend??) then you would have to allow Dry Ice to be a mineral on Mars.

Nigel Skelton
Tennant Creek - Australia



Minerals have: fixed composition, crystalline structure and are naturally occurring. Dry ice does not exist naturally on earth so it is no, strictly speaking, a mineral. But who knows what we will do when we find it naturally occurring on some moons of the outer planets of our solar system. A very interesting question. Dry ice from Titan would make an interesting addition to a mineral collection, would it not?

R. W. "Bob" Avakian
Instructor
Oklahoma State Univ. Inst. of Technology

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