Abstract <p>Niobian rutile [(Ti⁴⁺_0.614Nb⁵⁺_0.2Fe²⁺_0.034Ta⁵⁺_0.008Fe³⁺_0.136Zr⁴⁺_0.002)_∑0.994O₂] has been reported for the first time from the alkali feldspar rich pegmatite intruding the meta-sedimentary sequence of Kerala Khondalite Belt. This mineral [niobian rutile₁, (Ti⁴⁺_0.55Nb⁵⁺_0.236Fe²⁺_0.042Mn²⁺_0.002Ta⁵⁺_0.008Fe³⁺_0.152Zr⁴⁺_0.003)_∑0.993O₂] has exsolved to niobian rutile₂[(Ti⁴⁺_0.614Nb⁵⁺_0.2 Fe²⁺_0.034Ta⁵⁺_0.008Fe³⁺_0.136Zr⁴⁺_0.002)_∑0.994O₂], titanian nioboixiolite [(Ti⁴⁺_2.455Nb⁵⁺_0.801Fe²⁺_0.134Ta⁵⁺_0.032Fe³⁺_0.546Zr⁴⁺_0.006W⁶⁺_0.002Sn⁴⁺_0.003)_∑3.979O₈] which has equilibrated at a temperature close to ~632°C. Marginal ferrocolumbite [(Fe²⁺_0.621Mg²⁺_0.015Mn²⁺_0.228Ti⁴⁺_0.136)_∑01.00(Nb⁵⁺_1.706Ta⁵⁺_0.032Ti⁴⁺_0.186W⁶⁺_0.016Fe³⁺_0.017Sn⁴⁺_0.002Zr⁴⁺_0.035)_∑1.991O₆] has also been exsolved in niobian rutile₂. Mn is preferentially partitioned to ferrocolumbite. Micron size inclusion of uraninite has formed inside niobian rutile. The position of the Raman spectroscopic peaks in the niobian rutile matches with the pure rutile phase with the broadening of the peaks. The broadening of peaks has possibly occurred as a result of lattice distortion due to the incorporation of niobium (Nb), tantalum (Ta), and iron (Fe) in the structure. The Raman spectroscopic peaks produced for the titanian nioboixiolite in the present study are comparable to those of ixiolite and columbite but are methodically shifted to lower values and have broader FWHMs. The shifting was possibly caused by large proportions of lighter elements like Ti and Fe substituting for Nb in the lattice structure.</p> Research highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Niobian rutile [(Ti⁴⁺_0.614Nb⁵⁺_0.2Fe²⁺_0.034Ta⁵⁺_0.008Fe³⁺_0.136Zr⁴⁺_0.002)_∑0.994O₂] has been reported for the first time from the Kerala Khondalite Belt of Southern Granulite Terrain.</p> </ItemContent> <ItemContent> <p> Titanian nioboixiolite [(Ti⁴⁺_2.455Nb⁵⁺_0.801Fe²⁺_0.134Ta⁵⁺_0.032Fe³⁺_0.546Zr⁴⁺_0.006 W⁶⁺_0.002Sn⁴⁺_0.003)_∑3.979O₈] and marginal ferrocolumbite [(Fe²⁺_0.621Mg²⁺_0.015Mn²⁺_0.228 Ti⁴⁺_0.136)_∑01.00(Nb⁵⁺_1.706Ta⁵⁺_0.032Ti⁴⁺_0.186W⁶⁺_0.016 Fe³⁺_0.017Sn⁴⁺_0.002Zr⁴⁺_0.035)_∑1.991O₆] have also been exsolved in the same grain.</p> </ItemContent> <ItemContent> <p>Broadening of the Raman spectroscopic peak possibly occurred as a result of lattice distortion due to the incorporation of niobium (Nb), tantalum (Ta), and iron (Fe) in the structure.</p> </ItemContent> <ItemContent> <p>Large proportions of lighter elements like Ti and Fe substituting for Nb in the lattice structure of&#xa0;titanian nioboixiolite possibly caused a methodical shift of the Raman spectroscopic peaks to lower values with broader FWHMs.</p> </ItemContent> </UnorderedList></p>