H 2 



at 110 



S0 3 



35-46 



Fe 2 3 



37-46 



CaO 



trace 



N 2 



0-59 



K 2 



0-11 



Genth and Penfield — Contributions to Mineralogy. 201 



noticeable. Sections parallel to the pinacoid b, 010, show 

 under the microscope a strong action on polarized light, giving 

 an extinction at 16°-17° from the vertical axis in the acute 

 angle /3 above and behind. The pleochroism is very marked, 

 brownish red parallel to the extinction direction 16° from the 

 vertical axis and pale lemon-yellow at right angles to this. In 

 convergent polarized light this section yields no interference 

 phenomena. Hardness 25. Specific gravity 2*286. 



Amarantite occurs associated with, and sometimes imbedded 

 in a finely fibrous orange-colored mineral, probably siderona- 

 trite, also small quantities of limonite and quartz. The mate- 

 rial for analysis was selected from the best bladed masses ; it 

 seems to have been slightly contaminated with traces of ferric 

 hydrate. The fine powder is gradually decomposed by cold 

 Water into a basic insoluble salt. The quartz was deducted from 

 the analysis, which is as follows : 



I. II. III. Molecular ratio. Calculated. 



12-17 )„„.. 28-29 1-570' 7 28-250 



j 0-443 2 35-875 



37-09 0-234 1-05 35-875 



0-09 



These analyses give the formula : Fe 2 S 2 9 + 7H 2 0. 3 mole- 

 cules of water were lost at 110°. 



For comparison I give the analyses of A. Frenzel (loc. cit.), 

 J. B. Mackintosh (this Journ., Ill, xxxviii, 243), and L. Dar- 

 apsky (Neues Jahrb. f. Min., 1890, i, 55). 



Frenzel. Mackintosh. Darapsky. Calculated. 



H 2 27-62 [27-44] 28"33 2826 



S0 3 35-58 36-15 36-20 35"87 



Fe 2 3 - 37-26 35-69 3562 35-87 



A1 2 3 021 



Na 2 0-51 



Mr. Mackintosh states that at 110° 3*4:8 molecules of water 

 were expelled. 



2. Sideronatrite, A. Rairnondi.* 



The material which we have examined consisted of masses, 

 sometimes 70-80 mm in thickness, of a fine fibrous mineral 

 with pale orange to straw-yellow color. The little splintery or 

 prismatic crystals when examined with the microscope seem to 

 lie on a cleavage face and show in polarized light an extinction 

 parallel to their longer axis. They show a slight pleochroism, 

 pale straw-yellow for rays vibrating parallel to the longer axis, 

 almost colorless at right angle to this. In convergent polarized 



* Zeitschr. Kryst., vi, p. 633, 1882. 



