112 QUICKSILVEK DEPOSITS OF THE PACIFIC SLOPE. 



Both specimens are evidently essentially serpentine and the principal 

 difference is in the amount of ferrous oxide. 



While the comparison of these analyses with the slides of the specimens 

 from which they were made might seem sufficient to test the relations of the 

 chemical and optical properties, it was considered best to pursue the subject 

 somewhat further, because minute quantities of minerals other than serpen- 

 tine might escape detection in the anal5'sis. It seemed especially desirable 

 to establish the absence of talc and chlorite from the substances regardeu 

 as serpentine under the microscope. Talc, indeed, could not escape detec- 

 tion in flakes or grains of sufficient size to be submitted to optical examina- 

 tion, but it seemed possible that intimate mixtures of talc and serpentine 

 might be present, since talc is known to occur pseudomorphically after most 

 of the minerals which have been shown to be converted into serpentine and 

 after many more besides. Chlorite, on the other hand, shows a considerable 

 range of optical properties and bears some resemblance to serpentine. A 

 series of simple microchemical tests was therefore made upon the slides and 

 specimens. Serpentine is readil}' attacked by warm sulphuric or chlorhydric 

 acid, while talc is decomposed by neither and chlorite is not sensibly at- 

 tacked by chlorhydric acid. It was shown by the application of these tests 

 that the more vividlv polarizing serpentine did not differ in chemical behav- 

 ior from that which gives only gray tints between crossed nicols and that 

 the serpentine in the altered sandstones behaves exactly like the massive 

 serpentine. The optical discrimination between chlorite and serpentine was 

 fully confirmed, and no trace of an admixture of talc in the serpentine could 

 be duiected.' 



'A more detailed accoiiDt of these tests m;iy possibly be of interest to some readers, siuce the pub- 

 lished statements as to the behavior of these miueralsare iu part uot quite consistent and are in some 

 cases incomplete. The marmolitic serpentine of which an analysis has been given was found to be 

 slowly but completely decomposed by both chlorhydric and sulphuric acids when hot, a colloid mass 

 remainin*'. A slide of a serpentine from near Knosville, which showed great variation in the colors of 

 polarization, was uncovered, and a portion which gave brilliaut tints was cut oti'aud after washing in 

 alcohol was heated with a drop of sulphuric acid. The serpcntiue was completely decomposed, and on 

 partial evaporation prisms of magnesiuir; sulphate, extinguishing light at about 16^, and later hexag- 

 onal uniaxial scales were formed, as described by Professor Haushofer (Mik. Reactionen, p. 90). No 

 other salts were formed. To test the serpentine of the sandstones, specimen No. 57, Clear Lake, was 

 selected, because it contains a very remarkable pseudomorph, to be described hereafter. A portiou of 

 the slide was selected containing a quartz surrounded by supposed serpentine, from which distinct, 

 tooth-like projections penetrated the quartz. \ perforated cover was placed over this spot and the 

 balsam washed awav with alcohol. A minute drop of chlorhydric .icid was added and the slide heated 



