NO'lES on Phlogopyte. 75 



only a six-sided star will present itself, having in its center short lines, the 

 direction of which corresponds to the rays of the other system. See fig 1 {a d) 

 (be)(cf),ov(a> cV)(b> ei)(c<f>). 



A still thicker lamina shows sometimes only two lines, crossing each other at 

 90 degrees. The direction of those two lines corresponds to the lines b e and 

 b' t r \ or to any two perpendicular to each other (figure 1). 



It is the opinion of the writer that most of the phlogopyte laminae are built 

 up in the following manner : -| 1 (- . . . The (-J-) and ( — ) indi- 

 cate thin laminae, -j- being related in the plane (o) towards ( — ) for 90 degrees, 

 which will be partly confirmed by the examination under the micropolariscope. 

 On some laminae, the six-sided star is characterized by a stronger intensity of 

 one of its beams. / 



Laminae of phlogopyte, which were exposed for some time to a white heat, 

 showed asterism when cooled down again. Also cold, diluted acids did not 

 produce any change in regard to their asterism. 



Hardness.— B'<a$e (o) usually 2.5. Lateral faces harder, nearly 3., if the 

 streak is perpendicular to base (o). 



Spec. Gravity. — From 2.5 to 2.90. Specimens from Orange county, as an 

 average, 2.60. 



Streak. — White, grey. 



Electricity. — Laminae of phlogopyte rubbed with a woolen cloth become 

 electric ( — ). In breaking them or hammering them in a dark room, a number 

 of electric sparks will be seen. 



Chemical Composition.— -The following three analyses of Phlogopyte are 

 given in Dana's iMineralogy : 



' a. Na. K. H. F. 



- 4.94 7.23 0.95 Or awe. 



- 4.89 6.07 2.65 Crawe. 



14 trace 9.37 0.60 2.93 Ramm. 



Phlogopyte from Pope's Mills and Edwards, gave reaction of Manganase and 

 Fluorine. The writer detected Titanium in form of Menaccanite in examples 

 from the same locality ; and also obtained a strong reaction of oxide of iron. 



Alteration. — Phlogopyte usually undergoes metamorphic alteration to steatite. 

 Specimens from Yrooman's lake, St. Lawrence county, which have a fresh appear- 

 ance, have the interior corroded and marked with patches of steatite. In speci- 

 mens from Edwards, an alteration of phlogopyte to magnetite (menaccanite) goes 

 on — the first decomposing again to hydrated oxide of iron. 



Occurrence. — Usually with serpentine, limestone, and dolomite. In the 

 Swiss Alps it is found in dolomite with menaccanite. 



Mici oscopical examination. — Laminae of various degrees of thickness were 

 mounted in Canada balsam in the usual manner. Care was taken to press down 

 the bent lamina with the cover-glass, in order to have the whole lamina in the 

 plane of the objective glass. 



Phlogopyte of Orange county, viewed with a magnifying power of about 120 

 diameters, presents a clear light yellowish mass, through which various crystals 

 and enclosures are disseminated. 



The most prominent of these foreign particles consist of a number of long 

 primastic crystals, which have been already mentioned in the lines treating of 

 asterism. Sometimes these crystals are so similar in color to the phlogopyte- 

 basis itself, that they can only be detected by their outlines forming dark lines. 



Using polarized light for the following observations, the crystals will present 





Si. 



Al. Fe. Mn. Mg\ 



Edwards ... 



40.36 



16.45 29.55 



Edwards . . . 



40.36 



16.08 30.25 



Grouverneur, 



41.96 



13.47 .2.12 0.55 27.12 



