112 GEOLOGY AND PALEONTOLOGY. 



crystalline grains of quartz, in a paste of milky quartz. In many parts the granular structure 

 is seen passing into the homogenous texture. This sandstone is associated with the carboniferous 

 limestone. 



89. A reddish colored stratified rock ; apparently an altered shale becoming porphyritic. 



90. An argillaceous sandstone ; the granular structure gradually merging into a compact 

 chalcedonic mass. 



91. Conglomerate, associated with the preceding specimens, 89 and 90. The rock has the 

 aspect of a Tertiary conglomerate. 



92. A compact granular mass of feldspar and olivine. - 



93. A similar mass, colored by oxide of iron. The change of color perhaps due to infiltration 

 of heated water. 



94. Conglomerate, composed of quartz pebbleSj trap^ and other volcanic rocks, with much 

 calcareous matter. The pebbles are somewhat angular. (A modern product.) 



95. An earthy calcareous rock, associated with the preceding conglomerate. 



96. Compact dark colored trap rock. 



97. Talcous slate, with quartz veins. 



98. Granite, fine, granular, consisting of quartz, feldspar, and mica, in nearly equal proi)or- 

 tions, and having a more ancient aspect than the granite found associated with the trap rocks. 



These two specimens (from the same locality) give the first indications of an approach to 

 rocks of a character similar to those composing the Appalachian mountain chain ; and which 

 are like the products of metamorphic silurian strata. 



III. Specimens from the silver and lead-hearing rocks of the Corriletas. 



99. A compact silico- calcareous rock, with a few scales of mica. It appears to be an impure 

 subcrystalline limestone, and is associated with other specimens of limestone. This is repre- 

 sented as forming the rock traversed by the veins of silver-lead ore. 



100. Sulphuret of lead and silver. 



101. Sulphuret and carbonate of lead. 



102. Sulphuret of lead connected with a gray limestone. 



103. Earthy carbonate of lead, said to contain silver. 



104. Semi-crystalline limestone associated with the earthy carbonate of lead, which latter is 

 represented as occurring in beds or veins, distinct from the sulphurets. 



105. Limestone similar to the preceding, colored brown by oxide of iron. 



106. Compact, silicious limestone, which has undergone some alteration from igneous action. 



107. Compact, altered limestone, associated with the silver ores of the San Pedro mines. 



A specimen said to be associated with the silver of the San Pedro mine is a greenish, impure 

 limestone, with light colored or white crystalline points. The weathered surface presents 

 minute cavities, and it has altogether the appearance of an ordinary greenstone. On testing 

 by acids, it effervesces strongly, and is evidently highly calcareous. 



108. Cretaceous limestone containing shells of Exogyra, &c., from the foot of the mountain 

 in which the silver ores occur. 



The cretaceous strata overlie the upper carboniferous limestones, and are shown to have been 

 subjected to similar disturbances, so far as the elevation of the strata is due to such action. 



109. Red oxide and green carbonate of copper. — Copper mines of New Mexico. 



