Annual report of the State Mineralogist for the year ending ... . ter than at Carson, beingnearly vertical in places. A mile northeast of Agua Fria, there is aband of serpentine one thousand eight hundred feet wide. This extendsin a northwesterly direction a little past the middle of Sec. 7, T. 5 S.,R. 18 E., and terminates in long, irregular arms in the metamorphicslates. A continuation of this serpentine to the east forms the range ofhills which lies west of Mariposa Creek. This rock is by no meanshomogeneous; a specimen from the extreme southern end contains alarge amount of iron (76); anot
Annual report of the State Mineralogist for the year ending ... . ter than at Carson, beingnearly vertical in places. A mile northeast of Agua Fria, there is aband of serpentine one thousand eight hundred feet wide. This extendsin a northwesterly direction a little past the middle of Sec. 7, T. 5 S.,R. 18 E., and terminates in long, irregular arms in the metamorphicslates. A continuation of this serpentine to the east forms the range ofhills which lies west of Mariposa Creek. This rock is by no meanshomogeneous; a specimen from the extreme southern end contains alarge amount of iron (76); another, half a mile south of Mariposa, hasa fine granular structure (77). The surface of the serpentine is almostbare of vegetation, and two miles west of Mariposa affords a good oppor-tunity for study. There it contains numerous bodies of a massive,coarsely crystalline rock. These bodies are sometimes circular or ellip-tical, but more often in the form of narrow, discontinuous strata. Theyconsist of granular, serpentinous feldspar, and a light colored, scaly mass. of serpentine, in which the form and cleavage of the original pyroxenecrystals are preserved. No. 79 contains needle-like crystals of talc,altered from hornblende. Some are formed entirely of an altered feld-spar (80). In others, the large serpentinous pyroxene crystals form themajor part (81). The serpentine is often rendered schistose by thepressure to which it has been subjected, and the original pyroxene crys-tals are bent and drawn out into long, tough, and somewhat fibrousmasses (82). The schistose structure developed in the movements of theserpentine is of a peculiar, sinuous character: the laminae are small,curved, and lap past each other in the manner indicated in Fig. 3. The sides of the laminae are exceedingly smooth and shining, which,with the distorted crystals, indicate a long continued movement undergreat pressure (83). Nos. 84 and 85 are specimens of massive serpentine,in which the traces of former cryst
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Keywords: ., bookcentury1800, booksubjectgeology, booksubjectminesandmineralr
