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Albite, or soda-feldspar, a mineral which plays a more subordinate part than was formerly supposed, this name having been given to much which has since been proved to be Oligoclase. 3. Oligoclase, or soda-lime feldspar, in which soda is present in much larger proportion than lime, and of which mineral andesite are andesine, is considered to be a variety. 4.

Labradorite, or lime- soda-feldspar, in which the proportions of lime and soda are the reverse to what they are in Oligoclase. 5. Anorthite or lime-feldspar. The two latter feldspars are rarely if ever found to enter into the composition of rocks containing quartz.

Tridymite: 100.0 2.3. Orthoclase. Orthoclase. Albite. Oligoclase. Oligoclase. Labradorite. Labradorite. Anorthite. Anorthite. Leucite. Nepheline. Nepheline. Muscovite. Lepidolite. Li 4.85. Biotite. Biotite. Phlogopite. Margarite. Chlorite. Rapidolite. Talc. 63.00 .... .... trace .... 33.60 .... .... W 3.10 2.78. Tremolite. St. Actinolite. Hornblende. Uralite. Augite. Augite. Diallage.

The earliest volcanic eruptions occurred in the later Eocene epoch and were continued into the succeeding Miocene stage. These consisted of rocks moderately rich in silica, and are grouped under the heads of propylite and andesite. To these succeeded during the Pliocene epoch still more highly silicated rocks of trachytic type, consisting of sanidine and oligoclase trachytes.