Question

2. The chemical formula for biotite is K2Mg2ASİ,01 (OH) 2 Calculate the coordinator number for K. Using the table identify the positions of the K number of O ions surrounding the K ion? and O ions. Does your predicted value agree with the r minerals in the earth's crust are the silicate minerals. The basic building block for the silicate minerals is the silica tetrahedron. The tetrahedrons can be arranged in different ways to create the various classes of silicate minerals (Fig. 2). For each of the crystal models listed below, place the model in the correct silica te structure group. Explain why you placed the structure in the particular group.

Answer 1

1. Olivine - Coordination no. of Mg = 6

Coordination no. of Si = 4

2 Biotite - Coordination no. of K = 6

Coordination no. = Radius of smaller ion / Radius of larger ion

In biotite it is O^-2 to K^+1= .7 which is for 6 coordination no.

similarly we can calculate for Olivine also