Iron olivine

Taftp, J. Spence, J. C. H. (1982) Crystal lattice location of iron and trace elements in a magnesium-iron olivine by a new crystallographic technique. Science, 218, 49-51. 

An ortho-silicate of iron, termed fayalite or iron olivine, Fe2Si04, was first found on Fayal Island in the Azores. It had crystallised m tabular rhombs of Fe2Si04, very similar to the ferrous silicate present in certain slags.3 The axial ratios 4 are... 

Ferrous orthosilicate, iron olivine or Fayalite, Fe2Si04, occurs as tabular rhombs in iron slags, of which it is one of the commonest constituents. Its name is derived from Fayal Island (Azores), where it was first found, although probably even that specimen was originally a lump of slag from a ship s ballast. Its crystal elements are —3... 

Mikouchi T., Takeda H., Miyamoto M., Ohsumi K., and McKay G. A. (1995) Exsolution lamellae of kirschsteinite in magnesium-iron olivine from an angrite meteorite. Am. Mineral. 80, 585-592. 

Other industrially important basic products are forsterite and dolomite bricks. Forsterite bricks are manufactured by firing naturally occurring low iron olivine, a mixed crystal of 2Mg0 Si02 (forsterite) and 2FeO Si02 (fayalite). 

X. Kan, J.M.D. Coey, Mossbauer spectra, magnetic and electrical properties of laihunite, a mixed-valence iron olivine mineral. Am. Mineral. 70, 567-580 (1985)... 

The chondrules contained in the chondrites contain olivine, pyroxene, plagiok-lase, troilite and nickel-iron they can make up 40-90% of the chondrites. Chondrules are silicate spheroids, fused drops from the primeval solar nebula. Because of their differing constitution, chondrites are further subdivided one group in particular is important for the question of the origin of life, and has thus been intensively studied—that of the carbonaceous chondrites. 

Mixtures of iron and stone principally as the silicate mineral olivine, (Mg,Fe)2Si04, with additional Fe and Ni... 

Olivine is assumed to be the only mineral precipitating and the fa and fo subscripts refer to pure fayalite and forsterite. Upon crystallization of the incremental amount dM i of cumulate, the incremental amount dMfa of fayalite is precipitated, and, since the iron content of fayalite is constant... 

Fig. 5.2b gives results by Schott and Berner (1985) on the dissolution rate of iron-free pyroxenes and olivines, as measured by the silica release. 

Mossbauer spectra have been measured for various tektites, as well as for both natural and synthetic iron-bearing silicate minerals. These results are reported and compared with other similar studies available in the literature. The ratios of the intensities of the appropriate Mossbauer lines have been used to determine the ferric-ferrous ratios where possible. The spectra of the ferrosilite-enstatite series of pyroxenes show four lines which are interpreted as two quadrupole split doublets, and the ratio of the intensities of these lines indicates the degree of ordering in filling the available metal ion sites. Similar studies on the fayalite-forsterite series of olivines are also reported. 

The first extensive study of iron-silicate minerals published was by deCoster and co-workers (7, 24). Their results are summarized in Table VI. Augite is a pyroxene containing considerable Na and Ca. No iron percentage was given for the olivine studies. The other minerals are included for comparison. The values given here for biotite are averages for their three untreated samples, which have two sites described as distorted octahedra. Heat treatment at 700°C. for one hour resulted in the emergence of a new Fe peak in biotite. 

Present M sbauer Studies of Natural Pyroxenes and Olivines. Table IX gives the major element chemical compositions of the silicate minerals examined in this study. Table X compares the Mossbauer parameters of these minerals, while Figures 9-13 show representative Mossbauer spectra. Fayalite (Figure 9) is the only olivine in this group. The two lines are, however, somewhat broadened (0.35 and 0.39 mm./ sec.) compared with the width of natural iron foil lines observed with our source (0.24 mm./sec.) and suggest the near coincidence of two quadrupole-split doublets resulting from Mi and M2 sites. Analysis of this "two-line spectrum into a four-line spectrum in the manner described by Evans et al (11) could possibly yield parameters for the two iron sites, but this was not undertaken since both lines appear symmetric. The "two-line quadrupole splitting of 2.78 mm./sec. is somewhat smaller... 

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