Optical properties of lunar glass spherules from Apollo 14 fines

Rao, K. J. ; Cooper, A. R. (1972) Optical properties of lunar glass spherules from Apollo 14 fines Proceedings of the Third Lunar Science Conference, 3 . pp. 3143-3155.

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Optical spectra of lunar glass spherules are similar to observed spectra of silicate glasses containing both Fe2 + and Fe3 +. Increased absorption in the visible region upon heat treatment in the laboratory is attributed to an increased fraction of Fe3 +. From previous thermodynamic studies in sodium disilicate glass (Johnston, 1964) it is observed that below a fixed oxygen partial pressure the Fe2 + /Fe3+ ratio, at a given temperature no longer depends on oxygen pressure but is controlled by the disproportionation reaction 3FeO = Fe2O3 + Fe. It is suggested that among the consequences of this disproportionation reaction are (a) that the Fe2+/Fe3+ ratio in lunar glass may be a measure of the thermal history of the glass-this is supported by the fact that glasses of quite similar chemical composition show significantly different absorption coefficients in the visible-and (b) that the ability for the disproportionation to occur in the liquid and supercooled liquid phases may explain why iron metal is frequently found to be associated with the glassy phase. Birefringence which has been observed in rapidly heat-treated and quenched lunar glass spherules is shown to be explicable only on the basis of a chemical alteration, such as disproportionation or oxidation. Index of refraction changes which result on heat treatment of lunar spherules are not reconcilable with usual glass transition phenomena and hence also suggest chemical change.

Item Type:Article
Source:Copyright of this article belongs to Proceedings of the Third Lunar Science Conference.
ID Code:91175
Deposited On:16 May 2012 14:17
Last Modified:16 May 2012 14:17

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