Hillebrand and Washington — Minerals from Utah. 301 



von Kobell * and Church f . In general appearance it seems to 

 resemble tyrolite. It occurs in thin scales on quartz, but more 

 often in radiating scaly masses, somewhat like the pyrophyllite 

 from Graves Mt., Ga. It has a bright apple-green color, some- 

 times with a tinge of blue ; a somewhat pearly luster ; a hard- 

 ness of 2*5 (1/5-2 for tyrolite in the text books), and perfect 

 cleavage. Under the microscope it showed little or no pleochro- 

 ism and extinction parallel and perpendicular to the radial line. 

 In convergent light the cleavage flake showed the ordinary 

 biaxial figure with the dispersion p^>u. Its double refraction 

 is negative, the- acute bisectrix being perpendicular to the 



cleavage face, and coinciding with the crystallographic 6. The 

 obtuse bisectrix lies parallel to the radial direction of the crys- 

 tal, but whether it corresponds with a or b cannot be determined. 

 It was unfortunate that a crystallographic investigation was im- 

 possible, as our knowledge of tyrolite in this respect is of the 

 most meager description. 



On heating it flies into fine fragments, which by gentle 

 tapping of the tube collect into spongy masses. The mineral 

 melts in the flame of a Bunsen burner. 



The Sp. grav. of sample I (containing 2'25 per cent of in- 

 soluble gangue) was 3'27 at 20JC. From sample II, which 

 was the purest and best crystallized to be found, 125 per cent 

 of gangue has been deducted. 







I. 



Hillebrand. 



II. 



III. 



Pearce. 





a. 



6. 



Mean. 







CuO 



4520 



45-23 



45-22 



46-38 



42-60 



ZnO 







0-04 



0-04 



tr. 



0-97 (Fe 2 3 Alo0 3 ) 



CaO 



6-86 



6-82 



6-84 



6-69 



9-10 



MgO 



0-05 







0-05 



0-04 







As 2 5 



28-84 



28-73 



28-78 



26 22 



27-87 



P2O5 



tr. 





tr. 



tr. 





H 2 



17-26 







17-26 



17-57 



16-23 



S0 3 



? 



? 



? 



2 27 



2 45 



98-21 



98-19 



99-17 



99-22 



S0 3 was unfortunately not tested for in I. It may however 

 reasonably be assumed to be present in about the same amount 

 as in II, and if it be considered to be present as gypsum 

 (0aSO 4 , 2H 2 0) the following molecular ratios are obtained. 

 CuO (CaO) As 2 5 H 2 



I. 



5-00 



0-94 



6-80 



or 



11 : 



2-07 



14-96 



II. 



500 



0-84 



6-81 



or 



11 



1-85 



14-98 



III. 



5-00 



0-90 



6-29 



or 



11 



1-98 



13-84 



It appears herefrom that the A.s 2 6 is somewhat less and 

 the H 2 much less than required to satisfy the formula 5 CuO, 

 As 2 O s , 9H 2 0, derived from von Kobell's (1. c.) -analysis on the 



*'Pogg. Ann., xviii, 253. \ Journ. Chem. Soc, [2], xi, 108. 



