Tuesday
October 21, 2014

Homework Help: science(chem)

Posted by ~christina~ on Tuesday, July 31, 2007 at 9:51pm.

I'm totally confused with this topic..not sure if it's science or whatnot..

Pyrite/ fool's gold yep then comes the weirdness...I saw some jewlery sold as having "marcasite". But I do know from somewhere which I can't remember anymore that marcasite is actually pyrite. But when I looked up marcasite on wikipedia since I was curious on this topic, It said..very confusingly first of all in the first paragraph...

"The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2). Marcasite is often mistakenly confused with pyrite, but marcasite is lighter and more brittle. Specimens of marcasite often crumble and break up due to the unstable crystal structure, and it is this crystal structure that is the main difference between marcasite and pyrite. Though marcasite has the same chemical formula as pyrite, it crystallizes in a different crystal system, thereby making it a separate mineral. In jewelry, pyrite used as a gem is improperly termed "marcasite". This is wholly incorrect, as marcasite is never used as a gem.

Is this confusing or is it just me..the paragraph contradicts itself at the end...
can anybody explain this to me how Is marcasite or Is it Not pyrite?



I looked at "Fool's Gold" under Google.com and found the following. It is a little better understood than the reference you found in the same journal, Wikipedia.

Pyrite and marcasite

Pyrite is often confused with the mineral marcasite, a name derived from the Arabic word for pyrite, due to their similar characteristics. Marcasite is a polymorph of pyrite, which means it has the same formula as pyrite but a different structure and, therefore, different symmetry and crystal shapes. The formal oxidation states are, however, the same as in pyrite because again the sulfur atoms occur in persulfide-like pairs. Marcasite/pyrite is probably the most famous polymorph pair next to the diamond/graphite pair. Appearance is slightly more silver.Marcasite is metastable relative to pyrite and will slowly be changed to pyrite if heated or given enough time. Marcasite is relatively rare, but may be locally abundant in some types of ore deposits, such as Mississippi Valley-type Pb-Zn deposits. Marcasite appears to form only from aqueous solutions.

Pyrite is often used in jewellery such as necklaces and bracelets, but although the two are similar, marcasite cannot be used in jewelery as it has a tendency to crumble into powder.
note this Adding to the confusion between marcasite and pyrite is the use of the word marcasite as a jewellery trade name. The term is applied to small polished and faceted stones that are inlaid in sterling silver, but even though they are called marcasite, they are actually pyrite.

I trust this explains it all; i.e., it's a trade name.



It's false advertising...

Thanks Dr.Bob=D

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