A five-fold axis of symmetry is present in: a quartz c. tourmaline b. riebeckite d. none of these.

5 fold generally doesn't exist Quartz hexagonal system crystallization so 6 fold. tourmaline also 6 fold , and ribeckite monoclinic so 1 fold

Answer (D) None of these Five fold axis of symmetry doesn't exist in any crystal because five fold axis of symmetry can't produce a complete crystal lattice upon repetition. In na...