200 Lindgren, Hamilton, Palache — Melanovanadite 



finely divided pascoite. The residue gave a strong 

 sulplrur reaction in open tube and then dissolved in 

 HN0 3 giving a green color and strong vanadium reaction. 

 It was assumed, therefore, that a sulphide was present 

 and to determine it if possible many polished sections 

 were made. 



The polished sections showed in a dark gray gangue 

 one or two minute grains of pyrite, several minute grains 

 of hard greyish white color, not definitely determined. 

 Some bright scales of native copper were also observed. 

 The vanadium Avas present in the form of two minerals. 

 Minute prisms of melanovanadite were distributed 

 through the mass, clearly replacing the shale material 

 (largely gypsum). There were also veinlets of the same 

 substance. In oblique reflected light the melanovanadite 

 shows a blackish, submetallic luster, but in vertical illu- 

 mination it is rather bright greyish white with a tinge of 

 purple. It is very soft and gives a brown streak and is 

 instantly blackened by HN0 3 , HC1, and KOH. Included 

 in veinlets and masses of melanovanadite are irregular 

 masses of a metallic soft mineral of a brighter gray color 

 which undoubtedly is a vanadium sulphide though I am 

 not at all sure that it is patronite. The minute size and 

 fine intergrowth of the minerals tend to make a definite 

 identification difficult. The original vanadium mineral 

 was then a sulphide. Oxidation converted this to a blue 

 vanadyl sulphate (Minasragrite) which even now is abun- 

 dantly present in the mine water. Reaction with CaC0 3 

 in the water and further oxidation produced the calcium 

 vanadyl vanadate, melanovanadite, and the hydration of 

 the latter resulted in the orange-colored pascoite. The 

 process was carried out in the lower part of the oxidized 

 zone. 



The real patronite is a black mineral of fine grain and 

 metallic luster. In polished section it is shown to consist 

 of a very fine-grained mixture of three minerals. The 

 first and most abundant constituent is purplish gray and 

 is sometimes developed in rudely prismatic, thick forms. 

 The other two constituents are respectively light gray and 

 darker gray in color, and are developed in irregular 

 grains. All three minerals are doubtless sulpirides. 



The description given by Davy and Farnham (Micro- 

 scopical Determination of Opaque Minerals) does not 



