422 Butler and Schaller — Minerals from Beaver Co., I T /<t/i. 



or mine candlestick across the ore. If zinc sulphides are 

 present the point of the metal is followed by a line of sparks. 



Plumbojarosite. 



Phunbojarosite has previously been described from two 

 localities, first from Cook's Peak, N. M.*' and second from 

 American Fork, Utali.f 



Since this mineral has been so rarely noted, it was a matter 

 of some surprise to find it in no less than six mines and pros- 

 pects in Beaver County, in some cases in such abundance 

 that a considerable quantity could be picked from the ore 

 bins and dumps. The writer was told by one superintendent 

 that several tons of the mineral had been thrown on the dump 

 and later on being found to contain metal values had been 

 shipped to the smelter. ■ 



Plumbojarosite has been determined from the following 

 mines and propects in Beaver County : Horn Silver, Hub, 

 Moscow, Red Warrior, Harrington-Hickory, and an unnamed 

 prospect pit, and probably is present in still others. 



Occurrence. — The mineral is secondary, resulting from the 

 alteration of ore composed mainly of sulphides of iron, lead, 

 copper, and zinc. The secondary minerals for the most part 

 are the oxides, sulphates, carbonates and silicates of these 

 metals, and with these are plumbojarosite, frequently jarosite, 

 and other minerals in varying amounts. It is of interest to 

 note that from the Horn Silver mine three members of the 

 jarosite group were determined, namely, jarosite, plumbojaro- 

 site, and al unite. 



Physical properties. — As seen in the hand specimen, the 

 material is dark brown in color and distinctly micaceous in 

 appearance with a silky luster. Where the crystals are very 

 fine the micaceous character is less pronounced and the mineral, 

 if not examined with some care, might be mistaken for limo- 

 nite or some iron-stained material. Although the mineral is 

 frequently in rather large pieces as it comes from the mine, it 

 is readily crushed in the fingers and has an oily look and feel, 

 similar to fine graphite. Under the microscope the crystals 

 are seen to be thin hexagonal plates of a light golden-yellow 

 color. The crystals vary greatly in size but rarely exceed - 25 mm 

 in width. Measurement of the crystals has not been made 

 but they are undoubtedly hexagonal and so far as their proper- 

 ties have been determined they correspond to the material 

 examined by Wright from the American Fork locality. The 



* Hillebrand, W. F., and Penfield, S. L., this Journal, vol. xiv, p. 213, 

 1902. 



f Hillebrand, W. F., and Wright, Fred E., this Journal, vol. xxx, p. 191, 

 1910. 



