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 Post subject: Elements: Difference in major, minor, & trace
PostPosted: Fri Dec 28, 2018 1:36 am 
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Can anyone tell me what the "cut-off" is between what's considered a minor, major, and/or trace element?
I'm sure there are a ton of variables to contend with, to fully explain the question above, right?
It depends on the testing equipment being used, I'm sure, as well as the sample in question.
Or is the same basic equation used across all minerals/gems, regardless of its type?
What percentage of an element in a gem/mineral makes it considered a major constituent, as opposed to a minor.

Hypothetical Example: ....let's say anything under <0.01% is considered trace, and any element measured over that amount is considered a "minor/major element".(the cut off), then will that "cut off" be the same for ....say....beryl, or garnet, or zoisite, etc., as is for tourmaline?
I seen some folks use only "Major" and "trace", to describe things(scholastic papers), with no "minor" mentioned at all. Sometimes it doesn't require the extra distinction, I guess.
Are all species of mineral governed by the same "cut off", is part of what I'm trying to understand.
How many types of testing methods/machines, those commonly used in the major labs and university's, can test and make the distinction between trace and major/minor elements?

I hope it makes sense....sometimes I can't put pen to pad like I want to. #-o

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 Post subject: Re: Elements: Difference in major, minor, & trace
PostPosted: Fri Dec 28, 2018 2:33 am 
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I don't know that these terms are rigorously defined, though there is likely a rule of thumb.
Generally I think the distinction would have to do if you're dealing with a bulk constituent which has an established place in the chemical formula of this mineral because it's perfectly happy to slot into whatever site in the lattice it fits into, or if it's an element that's forced into a site it's not so happy in and thus can't make up a significant percentage of the composition (something that's easier to think of as a trace impurity than partial solid solution towards another compositional endmember). That's a bit loosey goosey though. I'd guess something around low single digits would be a rule of thumb cutoff?

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 Post subject: Re: Elements: Difference in major, minor, & trace
PostPosted: Fri Dec 28, 2018 2:41 am 
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probably this helps a little bit to understand:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=2ahUKEwjzp4-m9cHfAhXCZFAKHbrwC8UQFjAFegQIBRAC&url=http%3A%2F%2Felementsmagazine.org%2Fget_pdf.php%3Ffn%3Drossman.pdf%26dr%3De5_3&usg=AOvVaw2LD9nDEh0AMtjwvkKt3KFT

Here are some definitions:
https://www.mindat.org/glossary/minor_element
https://www.mindat.org/glossary/trace_element

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