Question

b and c please

Fayalite Coso Viths, CA Absorbance 500 2000 1000 1500 Wavelength, nm Almandine Wrangell 10 0260 4000 Wavelength, nm b) Based on the visible range of the absorption spectra above, explain why the colors of these two Fe2+ minerals are different. Keep in mind that the visible range is from 400 to 700 nm. (Olivine is yellow green and almandine is deep red) c) In olivine, Fetis in octahedral sites whereas in almandine, the Fe2+ is in distorted cubic sites. Based on site geometry and the geometry of d orbitals, explain how the crystal field splitting is different between olivine and almandine. Make a sketch to illustrate how site geometry effects splitting. (hint: the d2.2 and d.2 orbitals point toward the faces of the cube in the cubic site. See the lecture notes for crystal field splitting in cubic sites.)

Answer 1

Absorption spectrum 1: It absorbs in te violet range ( 380-450 nm) as per the spectrum provided for the Olivin ( Fayalite)

It is quite expected to observe the complimentary colour of violet for the olivin solution ( Violt- Yellow) which is yellow

Similarly the absorption spectrum of alamandine solution exhibit absorption at little above 500 nm ( 520-560 nm) that means it absorb green photon. We will observe the solution as deep red colour as red is te complimentary color of green.