Publisher's Synopsis
Excerpt from The Silica Refractories of Pennsylvania
Certain portions of the Chiekies formation from the Upper Cam brian in southeastern Pennsvlvania contain sufficient mica to justifv the name mica schist instead of quartzite, the name of the rock which comprises the greater part of this formation. Some bands of this mica schist make a very good refractorv because the rock will stand high temperatures, is durable and easily trimmed. The rock is reallv a highly metamorphosed quartzite with practicallv'all the. Aluminous impurities altered to muscovite the colorless mica. Here. The mica is not too abundant the fusibihtv of the rock is practicallv that of quartz because even though the mica fuses at a comparativeh low_ten1perature it simply glazes the surface of the rock and exerts ygi'v little in?uence on the fusibilit; of the rock as a whole. A fusion test on the rock showed that even thin edges on fragments (lid not fuse at. 1700°c. The melting point of cristobalite, the highest'temperature form of silica, is 1710°cl or bv the cone nethod of determining fusion points. - 1790°c.
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