[Rockhounds] Lepidolite and the micas

[Pmodreski at aol.com]

In a message dated 3/9/2008 6:19:11 AM Mountain Daylight Time,  
edwardjwagner at bellsouth.net writes:

Dear  Andrew Turner: The terms "ferrocolumbite and manganotantalite" are no 
longer  used, and have been replaced by the simple term "Niobium". This may 
sound  simplistic, but Columbite is considered an archaic term.  Often one sees  
the name "the Tantalum-Niobium end series", which includes all the "ferros,  
ferrics, manganos" and the other replacement metals that inhabit the  
aforementioned crystal structures. If one is familiar with what the names  represent, 
than it is easier to use a simple name. Edward  Wagner



Sorry, but this is not at all correct.  Niobium and tantalum are the  names 
of the chemical elements, not of the oxide minerals that contain them plus  Fe 
or Mn.
 
There is, however, a current controversy about the best and most correct  and 
accepted way to name these minerals.  The minerals containing,  repectivelyly 
Fe+Nb+O and Mn+Nb+O have up until now always been referred to as  
ferrocolumbite and manganocolumbite.  However, the latest (just published,  2008) edition 
of the book most commonly accepted as an authoritative source of  
scientifically correct mineral names, "Fleischer's Glossary of Mineral Species  2008", 
current editors Malcolm E. Back and Joseph A. Mandarino (the latter  recently 
deceased, in 2007) now gives the names of these two minerals as  columbite-(Fe) 
and columbite-(Mn).  This naming system has the virtue of  beginning with the 
name under which people would normally look for this  mineral--e.g., 
columbite--rather than, more confusingly, requiring people to  search for them 
alphabetically under "F" and "M".  However, this  change in nomenclature as espoused 
in this book edition also seems to have been  made somewhat unilaterally by the 
authors, because there has as yet been no  formal publication "authorizing" 
this new nomenclature under the approval of the  I.M.A. (International 
Mineralogical Association), and it has not met with  universal acceptance by the world 
community of mineralogical scientists.   So, the status of the "correct" 
names for the orthorhombic minerals FeNb2O6 and  MnNb2O6 seems to be, at this 
time, somewhat in doubt.  There is also an  analogous magnesium mineral, MgNb2O6, 
named either magnocolumbite  (traditional nomenclature) or columbite-(Mg) 
(proposed new system).
 
Turning to the tantalum-rich orthorhombic minerals in this family, the same  
situation applies; Fe2TaO6, MgTa2O6, and MnTa2O6 all exist, and are named 
either  ferrotantalite, magnesiotantalite, and manganotantalite, or 
tantalite-(Fe),  tantalite-(Mg), and tantalite-(Mn).
 
Well, at least one can say that it makes mineralogy a bit more interesting  
(though more confusing), having a debate and non-universal agreement as to how  
these (and quite a number of similarly disputed minerals) should properly be  
named.
 
Pete Modreski  (and, P.S., I'm going to correct the spelling of  "lepidolite" 
in the title of this thread!)
 



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