. Carnegie Institution of Washington publication. . i Fig. 25.—Microlites of oligoclase-andesine (AbgAnj). are instructive both on account of the exhibition of the habit of the feldspar crystals in these preparations and also as an evidence of the changes in habit during the short period of their growth. There are two types of microscopic crystals, one tabular, the other prismatic. These occur near one another intermingled in the glass. They are mm. long and smaller. In many cases there appears to be a nucleus of feldspar within feldspar; in some of these there are also small, irregularly
. Carnegie Institution of Washington publication. . i Fig. 25.—Microlites of oligoclase-andesine (AbgAnj). are instructive both on account of the exhibition of the habit of the feldspar crystals in these preparations and also as an evidence of the changes in habit during the short period of their growth. There are two types of microscopic crystals, one tabular, the other prismatic. These occur near one another intermingled in the glass. They are mm. long and smaller. In many cases there appears to be a nucleus of feldspar within feldspar; in some of these there are also small, irregularly shaped, colorless grains with rather strong index of refraction whose compo- sition is not determinable. These are extremely minute and not abundant. The feldspar nucleus exhibits stronger refraction than the marginal feldspar, but the direction of extinction is the same in both parts, proving like optical orientation and showing that the central part of the microlite is thicker than the margin and of the same composition. The initial crystal in these cases is thicker, that is, the crystallization. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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