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Entering other words/letters in formula

Posted by Jolyon Ralph  
Jolyon Ralph
Entering other words/letters in formula
August 18, 2002 02:18PM
Be careful when entering other letters and words in the formula field.

To take a recent example:

Alpha-Zn(OH)^2

would be incorrect, because the element-scanning algorithm that is needed for searching will take the first two letters of Alpha and assume that there is Aluminum in the mineral.

If you really need to add extra text to a formula, make sure it is all added as lower case only, so that it will not be detected by the system.

Similarly, for generic formula such as:

AB^2O^4

The A is fine, but the B would be detected as Boron.

Similarly, you can use X but Y would be regarded as yttrium.

Jolyon
Alan Plante
Re: Entering other words/letters in formula
August 19, 2002 04:40PM
Hi Jolyon

There are quite a few mineralogists who avoid using single letters that are abbreviations for elements when they write general formulas. There was even a paper written on this problem a few years back - I have a copy of it here.

Basically, any letter that is also used as the abbreviation for an element should NOT be used in general formulas. Not only will it confound a computer, it may confuse a meat-and-blood "computer" as well.

I have long been one of the "offenders" in this matter. I learned "A-B-C..." for cations, and "...X-Y-Z" for anions - and just plain haven't forced myself to un-learn it. But as I have been consulting with Joe M. on the Mineral Groups project, he has pretty much convinced me it is about time I changed my errant ways. My next editing cruise through the Groups list will see "B, C, ... Y" replaced with non-elemental letters.

[PS: That paper I mentioned above was correct in each and every one of its points, but went "a bridge too far" in its proposals for a standardized nomenclature for general formulas. (Too much in one gulp for people to swallow...) I have not seen it being adopted by authors - most likely because it simply went too far. But I hope that it will slowly gain acceptance and become the norm.]

Cheers

Alan
Alan Plante
Re: Entering other words/letters in formula
August 19, 2002 04:46PM
Oh yes -

Regarding the "alpha, beta, ... omega" issue; the convention recommended these days is to use it as a *suffix* - not a prefix. "Roselite-alpha," rather than "alpha-Roselite." And this recommendation is for just the reason you cite: It screws up computer searches when used as a prefix... As a suffix it is more "natural" to leave it uncapitalized - which prevents the computer recognition problem you note - and it won't screw up alphabetical sorts of mineral lists. "Roselite-alpha" ends up in the "Rs" where it belongs.

KOR

Alan
Jolyon Ralph
Re: Entering other words/letters in formula
August 19, 2002 06:27PM
I'll go through the alpha-minerals etc. changing them at some point!
Jolyon Ralph
Re: Entering other words/letters in formula
August 19, 2002 06:29PM
Oh, what would work is to use lowercase letters eg

a^2b^3SiO^4

The computer wouldn't get confused with that either.
Alan Plante
Re: Entering other words/letters in formula
August 19, 2002 09:01PM
Jolyon

That might not confuse the computer, but it would sure as heck confuse mineralogists - since "a", "b", and "c" are crystallographic axis symbols...

:~}

Probably best to just avoid letters that are also element symbols...


Alan
Jolyon Ralph
Re: Entering other words/letters in formula
August 19, 2002 09:45PM
agreed!

Jolyon
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