Infrared hydroxyl librational bands of talc-willemseite solid solutions (Mg–Ni talcs) have been explained by analogy with those of amphiboles. Two OH librational bands at 710 and 668 cm⁻¹ appear in talc-willemseite solid solutions, because the degeneracy of a single OH librational vibration in talc and willemseite end-members is lifted by the substitutions of their octahedral cations. Comparison of infrared spectra of natural and hydrothermally deuterated A site-vacant and Al^(IV) (tetrahedral Al)-free amphiboles reveals that two bands at 700 and 690–640 cm⁻¹ are also ascribed to OH librations.

抄録全体を表示

Ferromanganese oxide ores collected from three captive mines, viz., Koira, Kusumdih, Dengura, located in the western part of the Koira Valley, Sundargarh district, Orissa (India) have been investigated for their infrared absorption. Mineralogical assignment of the ore samples was made by infrared spectroscopic studies vis-a-vis XRD — microscopic interpretations. The common feature in all the IR Spectra is the presence of three major absorption bands in wave number regions of 1120–800, 710–410 and 350–250 cm⁻¹. The ores in general, exhibit three broad spectral patterns which when correlated with their respective composition are found to represent three categories of samples corresponding to high, medium and low grade types. The effect of temperature (calcination) on the characteristics of IR absorption spectra has also been discussed. The IR results have been of value in characterising the manganese ores of the Koira region in general.

抄録全体を表示

The morphology of zircon crystals synthesized by the flux method and doped with elements common in igneous rocks is described quantitatively, using a new method proposed by the first author. Within the experimental temperature range of 1150° to 1100°C, only {100} among the prism faces develops in all the zircons. The zircons doped with P or S show long prismatic habit, whereas non-doped zircons show a bipyramidal habit with very short prisms, and those with other doping elements a short-prismatic habit. As for the pyramid, {101} is exclusive in zircons doped with Ti, Al, Fe, P, S or U, and it is dominant in those doped with Ca, Mg, K, Na, Ni or Mn, with small {211} increasing in dimension in the same order. The effect of S and Mn, when mixed with other doping elements, becomes less distinct. The presence of P, however, always induces the formation of long prismatic crystals.

抄録全体を表示