40 F. R. Y an Horn — Pisanite and Arsenopy rite. 



Art. II. — Notes on a new occurrence . of Pisanite and 

 Arsenopyrite, and some large Staurolite Crystals from the 

 Ducktown District, Tennessee ; by Frank Robertson Van 

 Horn. 



Introduction. 



During the month of June, 1912, the writer spent about 

 three -weeks with a class of Case mining students in the vicin- 

 ity of Ducktown, Tennessee. While visiting an abandoned 

 open cut of the Ducktown Copper, Sulphur, and Iron Com- 

 pany at Isabella, considerable amounts of a sulphate deposit 

 of secondary origin were observed. These minerals were col- 

 ored green in some places, but blue was the prevailing color 

 for most of the formation. It was at first thought that the 

 green mineral was melanterite (FeS0 4 + 7H„0), and that the 

 blue substance was chalcanthite (CuS0 4 + 5H 2 0). However, 

 the green deposit was rubbed with a knife blade which was 

 immediatel} 7 colored by the precipitation of copper, which 

 proved that the mineral could not be melanterite. Subsequent 

 tests and analyses showed that neither melanterite or chalcan- 

 thite were present, but that both the green and blue minerals 

 were pisanite with varying proportions of iron and copper. 

 Since pisanite has never been reported from the region, as far 

 as the author is aware, the new occurrence has been thought 

 worthy of record. 



Pisanite. 



As has been previously stated, the mineral was found in two 

 varieties, green and blue, on the walls of an abandoned open 

 cut at Isabella, Tenn. This locality is situated about one and 

 one-half miles east-southeast of Ducktown. A view of the 

 open cut workings is shown in fig. 1, in which the light-col- 

 ored deposit along the right hand wall consists of pisanite. 

 The blue variety is found in greater abundance than the green 

 mineral. Both substances are transparent and are found as 

 crusts, botryoidal coatings, and stalactites on the walls of the 

 cut, which consist chiefly of pyrite with some pyrrhotite and 

 chalcopyrite. Fig. 2 is a nearer view of the occurrence shown 

 in fig, 1. In fig. 2 some small stalactites are visible, and the 

 botryoidal appearance can also be noticed. Limonite has pre- 

 cipitated in large amounts from the water to be seen in the 

 lower right hand corner of the picture, and the water is quite 

 highly charged with copper. In some places the deposits are 

 more or less hollow, and the cavities show distinct crystals. 

 Many specimens were collected, and no change was noticed in 

 their appearance until after six months when the surface of 

 practically all pieces became white and opaque. 



