456 



walker: crystal form of spencerite 



Gold, amorphous Au 



Sodium, dispersoidal Na 



Potassium, dispersoidal K 



Calcium, dispersoidal Ca 



[Occurrence in nature reported by Cornu, 

 Z. Chern. Ind. Kolloide, 4: 187. 1909. 

 (Not in Dana.) 

 First suggested by Elster and Geitel to 

 be the cause of color of blue halite, Ann. 

 Phys, Chem., 62: 559. 1897; this has been 

 confirmed by ultramicroscopic study 

 and by successful synthetic experiments, 

 as shown especially by Goldstein, 

 Nature, 94: 494. 1914. (Not in Dana.) 



[Suggested to be the cause of color of blue 

 sylvite, by analogy with the preceding 



j substance, by Cornu, Centr. Min. 

 Geol., 1907, 168; this has been con- 

 firmed as in the preceding instance. 

 (Not in Dana.) 

 Suggested to be the cauce of color of cer- 

 tain fluorites by Doelter, Sitzungsb. 

 Akad. Wiss. Wien, 1908, 1312. (Not in 

 Dana.) 



MINERALOGY. — The crystal form of spencerite. T. L. Walker, 

 Royal Ontario Museum of Mineralogy, Toronto. 



The new mineral spencerite — Zn 3 (P0 4 )2. Zn(OH) 2 . 3H 2 — was 

 described by the author in 1916. 1 The material then available 

 was obtained from the H. B. mine near Salmo, British Columbia. 

 It is remarkable for its purity but is wholly in the massive form. 

 From an optical examination it was found to be monoclinic and 

 polysynthetically twinned, the twinning plane and composition 

 face being the orthopinacoid. Plates parallel to the best cleav- 

 age, accepted as the orthopinacoid, showed an interference figure 

 with the acute bisectrix nearly normal to this cleavage. Such 

 plates when etched yielded etch figures symmetrical about only 

 one plane. From these observations the author concluded that 

 the mineral is monoclinic. 



Spencerite occurs along with other oxidized zinc ores, forming 

 the cores of stalactitic growths, the outer zone of which is always 

 calamine. The spencerite being relatively soluble, the periphery 

 of the spencerite core has as a rule been dissolved, leaving a 

 space between the more soluble core and the resistant calamine. 



1 Mineralog. Mag., 18, p. 76. 



