52 CALIFORNIA ACADEMY OF SCIENCES. 



small quantity; feldspar, nepheline and leucite are absent. 



Although the examination seemed to indicate that the 

 analcite was primary, I hardly ielt myself warranted, 

 with the evidence in possession, to make an assertion so 

 opposed to the dogmas of petrography, and upon finding 

 that some of the rocks contained a trace of sulphuric acid 

 expressed a surmise that the mineral in question might 

 have been derived from noseane or a related mineral of 

 the sodalite group, — at the same time, however, mention- 

 ing the remarkably primary appearance of the analcite. 



After a thorough re-examination of the slides and the 

 rocks with such scanty material as remained to me, this 

 view no longer seems tenable, and I think the probability 

 very great that the mineral is primary analcite, or pos- 

 sibly a primary mineral very closely related to analcite. 



It does not, indeed, seem impossible to obtain a hydrous 

 silicate from a magma in aqueous fusion, provided the 

 process of solidification were carried on slowly and under 

 sufficient pressure. That hydrous substances can solid- 

 ify from a molten magma is already proved by the un- 

 doubtedly primary water, which is so often found in old 

 and recent volcanic glasses. Moreover, analcite is a 

 mineral which may be formed and exist under high pres- 

 sure and quite high temperature, as shown by Friedel 

 and Sarasin, who produced artificial crystals of analcite 

 at a temperature of 400° and high pressure.* 



The typical analcite basalts are dark green rocks, por- 

 phyritic by dark green long augite prisms and abundant 

 small round crystals of a whitish color. Occasionally the 

 olivine is also visible. In thin section the augite appears 

 as long octagonal prisms with good cleavage and normal 

 extinction; the Color is light green in transmitted light, 

 usually darker green toward the periphery, or the crystals 



"Sur la reproduction de I'albite par voie aqueuse. C.R. 1883, xciii, 5, p. 290. 



