FA I N HANKS.] 



. I nalcite Diabase. 



297 



secondary spherulites except chalcedony would resist the action of 

 acids, and these cannot be referred to that substance. 



EAGLE RANCH OCCURRENCE. * 



A small dike, which should undoubtedly be classed with the 

 analcite diabases above described, is found on the Eagle Ranch, in 

 the heart of the Santa Lucia Range. It outcrops in the center of 

 a conical hill, formed of lower Cretaceous sandstone and shale. 

 Microscopically it very closely resembles the secondary dikes of 

 the Cuyamas eruptive, but is more decomposed, no analcite being 

 visible. The feldspar has a dull luster, but the augite appears quite 

 fresh. Much greenish material is scattered through the rock. The 

 structure is diabase granular. 



Microscopically the specimens appear very much decomposed. 

 The short lath-shaped feldspars show traces of polysynthetic twin- 

 ning, but are completely decomposed to cloudy kaolinic mask's. 

 It is not possible to measure the extinction angle. The augite is 

 fresh in some specimens, in others considerably clouded. It 

 has a pale brownish color, and shows no pleochroism. A pale 

 green substance, somewhat fibrous, is very abundant in the thin 

 section. It fills angular areas between the feldspars, and in many 

 cases has invaded the latter. This substance closely resembles that 

 which has replaced the analcite in the more altered of the dikes 

 already described. In its manner of occurrence it is precisely 

 similar. No analcite was detected in any of the specimens, but 

 there seems to be no doubt about its original presence. Secondary 

 feldspar appears quite frequently on the borders of the green areas. 

 Magnetite is present in the form of skeleton crystals. 



None of the specimens exhibit any peculiarity not before 

 described, and, owing to the extreme degree of decomposition, a 

 more detailed description will not be attempted. 



CONCLUSION. 



No rocks of the character of those described in this paper have 

 been noted before on the Pacific Coast, while none so closely related 



*The writer's attention was called to this dike through the kindness of 

 A. F. Benton, superintendent of the Eagle Ranch. 



