Calcium carbonate sample -> calcite or aragonite?

[Picasso]

Calcium carbonate sample --> calcite or aragonite?

Is there a definite way to determine whether a calcium carbonate sample is calcite or aragonite? The weak bond of aragonite should produce an active reaction with a weak acid such as diluted acetic (vinegar), whereas calcite will require a stronger acid to produce an active reaction. Is this a valid test?

 

[PAllen]

Is there a definite way to determine whether a calcium carbonate sample is calcite or aragonite? The weak bond of aragonite should produce an active reaction with a weak acid such as diluted acetic (vinegar), whereas calcite will require a stronger acid to produce an active reaction. Is this a valid test?

A powdered sample or a crystalline sample?

 

[Picasso]

Consistency of sand.

 

[PAllen]

Consistency of sand.

Well you can try a look with modest power microscope e.g. 20-40x. If you can see any well defined crystal forms, it should be possible to distinguish by inspection since calcite and aragonite have different crystal forms. If you don't see any well defined crystal structures, then ... I can't help. You need a chemical test, x-ray test, areas I'm not familiar with.

 

[Picasso]

Found a definite chemical test using Feigl's solution:

http://www.mindat.org/mesg-100-179708.html