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_(
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 ?
A. `CaAl_(3)Fe_(6)(BO_(3))_(3)S_(6)O_(18)F_(4)`
B. `Ca_(2)Li_(3)V_(6)(BO_(3))_(3)Si_(6)O_(18)(OH)_(4)`
C. `KMg_(3)Cr_(6)(BO_(3))_(3)Si_(6)O_(18)F_(4)`
D. `CaAl_(9)(BO_(3)_(3)Si_(6)O_(18)(OH)_(4)`
1 Answers
Correct Answer - A
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`