Tourmalene is a class of cyclosilicates with general formula. (Ca, K, Na) (Al, Fe, Li, Mg, Mn)_(3)(Al, Cr, Fe, V)_(6) (BO_(3))_(3) (Si, Al, B)_(6)O_(18)(OH, F)_(4) Which of the following is not a correct example of tourmalene ?

Tourmalene is a class of cyclosilicates with general formula. (Ca, K,

1.	Tourmalene is a class of cyclosilicates with general formula. (Ca, K, Na) (Al, Fe, Li, Mg, Mn)_(3)(Al, Cr, Fe, V)_(6) (BO_(3))_(3) (Si, Al, B)_(6)O_(18)(OH, F)_(4) Which of the following is not a correct example of tourmalene ?
Answer» `CaAl_(3)Fe_(6)(BO_(3))_(3)S_(6)O_(18)F_(4)` `Ca_(2)Li_(3)V_(6)(BO_(3))_(3)Si_(6)O_(18)(OH)_(4)` `KMg_(3)Cr_(6)(BO_(3))_(3)Si_(6)O_(18)F_(4)` `CaAl_(9)(BO_(3)_(3)Si_(6)O_(18)(OH)_(4)` Solution :You are not expected to have a PRIOR knowledge of tournaline.It is simply a common-sense based question based on adding all the CHANGES. `(1)+2+3xx3+x xx 6-3xx3+4xx6-2xx18-1xx4` `=6 xx -14 ne 0` for `x=+2` or `+3` (possible on FE) `(2)+2xx2+1xx3+3xx6-3xx3+6xx4-18xx2-1xx4=0` it fits so it is possible `(3)+1xx1+2xx3+3xx6-3xx3+4xx6-2xx18-1xx4=0` `(4)+2xx1+9xx3-3xx3+6xx4-2xx18-1xx4=0`