3.17. (a) Talc, Mg3(OH)2(Si2O5)2, is slippery. Based on its structure why is that? (b) Consider the following two micas: CaAl2(OH)2(Si2Al2)O10 and KAl2(OH)2(AlSi3)O10. The Mohs hardness of one of them is double the other. From your knowledge of their chemistries and structures, which one do you conclude would be the harder mineral. Explain your rationale. (c) Along the same lines where do you think the hardness of the mineral pyrophyillite, Al2(OH)2(Si2O5)2, falls in comparison to the micas in part (b)? Explain your rationale