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PLATE XVIII. 
Photomicrographs of Ores. 
A. Quartz veinlet with radial structure in breccia, Empire State mine, level 10; crossed nicols. Magnified 
28 diameters. 
B. Phenocrysts of orthoclase in latite-phonolite, Gold Sovereign mine, level 7, showing sericitization. Lighter 
central areas indicate abundant microcrystalline aggregates of seric.ite, while in the darker periph¬ 
eral spaces more feldspar remains. Black areas indicate pyrite. On veinlets and in small spaces 
of dissolution adularia has developed. Crossed nicols. Magnified 28 diameters. 
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