26 GEOLOGY. 



No. 23. A compact, white, feldspathic rock, from tlie valley of the San Pedro river, in Sonora. Before the blow-pipe it 

 exhibits all the reactions of a felsite or fine-grained porphyry. The texture is comp.oct, resembling the base of porphyry without 

 the crystals. The surface exhibits numerous small cavities, resulting, perhaps, from the decomposition of crystals of feldspar. 

 No. 24. A yellowish pulverulent substance, described by Dr. C. B. R. Kennerly as occurring in a mountain gorge be- 

 tween abrupt walls of volcanic rock. When treated with acid it effervesces strongly, showing the presence of carbonate of 

 lime. After the effervescence has ceased, the residue does not seem to be much acted upon by hot concentrated acids. Before 

 the blow-pipe it fuses with difificulty to a white enamel, owing probably to a combination, at this high temperature, of the 

 silica and lime present. Water takes up from it a considerable quantity of saline matters, consisting of sulphates of lime 

 and magnesia, with traces of chloride of sodium and chloride of potassium. If this be a volcanic ash, as its appearance and 

 mode of occurrence suggest, the presence of the saline matter and carbonate of lime must he attributed to the subsequent 

 action of mineral, probably thermal, springs containing these salts in solution. 



Very respectfully, yours, 



JOHN D. EASTER, 

 Ph. D. , Chemist and Mineralogist. 



Smithsonian Institution, Washington, Ajtril 11, 1856. 



SiE : I have the honor herewith to report the result of my examination of the ores and coals submitted to me for 

 analysis. Those the locality of which is not given belong to the collection obtained by you from a "prospecter," who 

 refused to reveal the precise locality in which they were found. The rest were collected by Mr. A. Schott. 



No. 1 is a lignite taken from cretaceous strata, covered by trap, at Santa Rosa, Coahuila. The specimen has a brilliant 

 lustre, even fracture, and shows no trace of woody structure. The streak is brown. Jt is free from pyrites. Fragments 

 of it heated to redness In a closely covered crucible lost 30.45 per cent, of water and bitumen, leaving 69.55 per cent, of 

 coke, which was very porous and had a brilliant metallic lustre. The same specimen completely incmerated yielded 24.22 

 per cent, of ash. 



No. 2. Lignite ; a dull, lustreless specimen, otherwise quite similar to the preceding. Treated in the same way, it yielded 

 51. 2 per cent, of coke, and 16. 8 per cent, of ash, of a reddish color. No pyrites was observed in it. 



No. 3. Lignite ; in all respects similar to the preceding. It gave 45. 5 per cent, of coke, and 15 per cent, of ash. This 

 is the best of these coals. The great amount of ash which these specimens contain renders them of little value as fuel 

 where wood can be had, but in the treeless region where they occur they may he very useful if the beds are extensive and 

 occur at a small depth below the surface ; aS the specimens were probably taken from the outcrop, it is not unlikely that 

 the seams, when further worked, wiU improve in quality. 



No. 4. A lignite from Lake Guzman, in Chihuahua, containing a large proportion of iron pyrites, which, by the action of 

 the atmosphere, has heen decomposed and converted into sulphate of iron. It is entirely worthless. 



No. 5. Water-worn pebbles of red oxide of iron, mixed with much silica, from Los Nogales, near the intersection of the 

 parallel 31° 20' north latitude, with the 111th meridian. The specimen which I assayed yielded 32 per cent, of iron ; the 

 assay was made by Penny's process, with bichromate of potash. 



No. 6. Two small specimens of red hematite, mixed with specular iron ore and quartz, yielding 37 per cent, of iron. 



No. 7. Carbonate of lead, associated with earthy black oxide of magnesia and iron ochre. This is a very unusual associ- 

 ation of minerals. The magnesia contains no cobalt, as is the case in a similar ore occurring at Mine la Motte, in Missouri. 

 The specimen yielded, in an assay conducted in the wet way, 17. 04 per cent, of lead. 



No. 8. Malachite, (carbonate of copper,) enclosing a core of red oxide of copper, containing a few particles of native 

 copper. It yielded 67. 76 per cent, of copper. 



No. 9. Red oxide of copper, containing a considerable proportion of native copper, in threads and crystals. The speci- 

 men is created superficially with malachite, and is precisely simUar to the ore No. 19, from Boca Grande, described in my 

 former report. It will yield about 96 per cent, of copper. 



No. 10. A specimen of black oxide of copper, associated with silicate of copper and silica. The mean of two assays gave 

 50 per cent, of copper. 



No. 11. Black oxide of copper, mixed with some sulphuret of copper and quartz, from the Sierra Tule, in Sonora. This 

 is very similar to the last specimen. It yielded 57. 66 per cent, of copper. No silver was found in it. 



No. 12, Red oxide of copper, associated with malachite and small particles of native copper, from the Arizona mines, in 

 Sonora. The mean of two assays gave 74. 96 per cent, of copper. 



No. 13. A compact silicious ore, containing galena, sulphurets of copper, and arsenical pyrites, intimately mixed with 

 quartz and calcareous spar. It yielded, in an assay conducted in the wet way, 41. 84 per cent, of lead ; 0. 12 per cent. sUver; 

 and 2. 8 per cent, copper. 



No. 14. Galena, associated ^vith variagated sulphuret of copper, carbonate of lead, and quartz. Very slight traces of 

 silver were detected by hydrochloric acid. The specimen yielded 50. 4 per cent, of lead, and 4 per cent, of copper. 

 I have the honor to remain, very respectfully, yours, 



JOHN D. EASTER. 



