Editing Goldschmidt classification (section)

==Trace and synthetic elements==
[[Synthetic elements]] are excluded from the classification, as they do not occur naturally.

Trace radioactive elements (namely Tc, Pm, Po, At, Rn, Fr, Ra, Ac, Pa, Np, Pu) are also treated as synthetic. Although these do occur in nature,<ref>{{cite book |last1=Yoshida |first1 = Zenko|first2 = Stephen G.|last2 = Johnson|first3 = Takaumi|last3 = Kimura|first4 = John R.|last4=Krsul|ref=Yoshida et al.|contribution = Neptunium|title = The Chemistry of the Actinide and Transactinide Elements|editor1-first = Lester R.|editor1-last = Morss|editor2-first = Norman M.|editor2-last = Edelstein|editor3-first = Jean|editor3-last = Fuger|edition = 3rd|date = 2006|volume = 3|publisher = Springer|location = Dordrecht, the Netherlands<!--|pages=703–4-->|pages = 699–812|url = http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|doi = 10.1007/1-4020-3598-5_6|archive-url=https://web.archive.org/web/20180117190715/http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|archive-date=January 17, 2018|isbn = 978-1-4020-3555-5}}</ref><ref name = "Cigar">
{{cite journal
|journal = Geochimica et Cosmochimica Acta
|volume = 63|issue = 2|pages = 275–285
|date = 1999
|doi = 10.1016/S0016-7037(98)00282-8
|title = Nature's uncommon elements: plutonium and technetium
|first1 = David
|last1 = Curtis
|last2 = Fabryka-Martin |first2=June |last3=Paul |first3=Dixon |last4=Cramer|first4=Jan
|bibcode=1999GeCoA..63..275C
|url = https://digital.library.unt.edu/ark:/67531/metadc704244/}}</ref><ref>{{Ullmann|volume=31|page=188|last1=McGill|first1=Ian|contribution=Rare Earth Elements|doi=10.1002/14356007.a22_607}}</ref> their occurrence is dependent on their [[Parent nuclide|long-lived parents]] Th and U, and they are not very mobile. For instance, [[polonium]]'s chemistry would predict it to be a chalcophile, but it tends to occur instead as a lithophile along with its parent [[uranium]]. Even [[radon]], a gas at [[standard conditions]], does not usually have time to travel very far from the original uranium source before decaying. When needed, these elements are typically produced synthetically in [[nuclear reactors]] instead of extraction from ores.