Co-orthopyroxene

Hawthorne, F. C. Ito, J. (1977) Synthesis and crystal structure refinement of transition metal orthopyroxenes. I. Orthoenstatite and (Mg,Mn,Co) orthopyroxene. Canad. Mineral., 15, 321-38. 

Recently, Evans and co-workers (11) studied the spectra of three orthopyroxenes with Fe/(Mg + Fe) ratios of 0.758, 0.532, and 0.280. They obtained two somewhat asymmetric lines, and their results are summarized in Table VIIIA. One of these authors had previously established by x-ray analysis (12, 13) that the sample with the 0.532 ratio exhibits Mg-Fe ordering, with iron preferring the larger, more distorted M2 site. Consequently it was concluded that the two-line Mossbauer spectra must consist of a superposition of two quadrupole-split doublets nearly coinciding. Mossbauer parameters for iron in these... 

Grandstalf D. E. (1977). Some kinetics of bronzite orthopyroxene dissolution. Geochim. Cos-mochim. Acta, 41 1097-1103. 

Fig. 12. Fischer-Tropsch reaction at 1 atm is first-order in CO, with an activation energy of 27 kcal/ mole (Lancet, 1972). Rate in a flow system is 10 times faster than in the static system used here. Dashed line shows extrapolation to solar nebula, assuming that the rate is proportional to (PcoIIPhj) . Reaction proceeds at an undetectable rate when the Bruderheim L6 chondrite is used as a catalyst. Apparently the high-temperature minerals in this meteorite (olivine, orthopyroxene, troilite, and nickel-iron) do not catalyze the hydrogenation of CO. Thus CO can survive in the solar nebula down to 400 K, when catalytically active minerals first from (Fig. 1 and 10)...

---