Please see the attached files. I will upload a worked example shortly. Hope this helps. You can refer the text: Petrochemical Calculations by Conrad Burri if available, from which the uploaded materials were prepared.

Follow the given link for worked out examples.

etheses.dur.ac.uk/9200/1/9200_6131.PDF

Dear Jayabalan Manickam 

Thank you for the information and links.

Dear Akram Mirlohi,

              You are welcome.

I had the same question. Thank you for uploading those texts.

But, anyway, are these "Niggli Values" still used today? Are they still good parameters of  geochemical association of rocks?

     Not today,but the petrological literature (mostly from Europe) till the mid to late seventies have used Niggli values for both igneous and metamorphic rocks. It would not be surprising if they are still used today. Niggli primarily used the values to describe magmas and not rocks. The Niggli norm/Barth Niggli norm is better than the CIPW norm, as it applicable to both metamorphic and igneous rocks. Certain parameters, for example, 'mg' approximates the Mg#, 'k' - alkalinity ratio, and 'w' - to calculate the oxidation of iron, are still useful.

     Are they still good parameters of geochemical association of rocks? Yes, if you construct a Niggli variation diagram and apply the interpretation indices devised by Niggli (as detailed in Petrochemical Calculations by Conrad Burri). The Niggli variation plot has the same limits as a Harker variation diagram - mainly applicable to co-magmatic rocks and set of lavas from a single volcano.   

Thank you very much, professor Manickam.

I'm working with some para-amphibolites, and almost all the literature that i've found is from this period (1950-1980), and the interpretations are based mainly in Niggli Values

Dear Guilherme Ferreira da Silva,

You are welcome.