. Carnegie Institution of Washington publication. OXIDES. !7 maxima, at an^ I3-1 ,u> respectively. The reflecting power decreases uniformly from 12 per cent at 4 ta to 10 per cent at 8 p, passes through a minimum of 4 per cent at /<, then suddenly rises to 78 per cent at Rutile (TiO,). (Graves Mountain, Lincoln County, Georgia. Curve b, fig. 9.) The surface of the specimen examined was a natural crystal face, area about by cm.,having a high polish, but uneven and containing cracks. The reflection curve is the most unusual of all examined in that the band of se
. Carnegie Institution of Washington publication. OXIDES. !7 maxima, at an^ I3-1 ,u> respectively. The reflecting power decreases uniformly from 12 per cent at 4 ta to 10 per cent at 8 p, passes through a minimum of 4 per cent at /<, then suddenly rises to 78 per cent at Rutile (TiO,). (Graves Mountain, Lincoln County, Georgia. Curve b, fig. 9.) The surface of the specimen examined was a natural crystal face, area about by cm.,having a high polish, but uneven and containing cracks. The reflection curve is the most unusual of all examined in that the band of selective reflection occurs almost at the working limit of a rock- salt prism. The maximum is broad and is fairly well defined at ft. 80%. 3 4 5 6 7 8 9 10 II 12 13 Fig. 9. — Wulfenite (a); Rutile (6); Zincite. 14 ISfl Zincite (ZnO). (From Franklin, New Jersey. Curve c, fig. 9.) The specimen examined was massive, having a red color and a dull polish. The surface was full of cracks, which would materially reduce the reflecting power. The reflecting power is low and uniform throughout the region of the spectrum examined. No bands of selective reflection were found. In this respect zincite is similar to iron oxide, but, on account of its low reflecting power, it is to be classed with the " insulators," and hence one would expect to find bands of selective reflection in the infra-red. Corundum (AI2O3). (Craigmont, Renfrew County, Ontario. Curve b, fig. 10.) This specimen was an opaque crystal, of which a cleavage surface, about 2 by 3 cm. in area, was examined. The surface contained striae, but otherwise had a high polish. The reflecting power is unusually low, except in the region of selective reflection, when it is quite high. The region of selective reflection is wide with maxima at , , and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these
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