SOHAI.LER.] 



Minerals from Leona Heights. 



VM 



This gives the formula, FeS0 4 + 7 H 2 0. 



According' to fractional water determinations, y of the water 

 is given off at a temperature of about 110°, while a. temperature 

 above 200° is necessary to drive off the remaining molecule. 

 It would thus seem as if the last molecule might be consid- 

 ered as constitutional, only six molecules being water of 

 crystallization. Following the suggestion of Prof. Reinsen,* the 

 structural formula for melanterite may be written, 



General Description. — The most a' mndant secondary mineral 

 occurring in the mine is pisanite. Long prisms of this mineral 

 are seen almost everywhere and large magnificent specimens arc 

 rather abundant, especially near the mouth of the northern tun- 

 nel. Unfortunately, on the slightest jarring most of the crystals 

 readily detach themselves from the rock. Many of the crystals 

 seem to have formed directly on the rock and were lying 

 loose; unattached. Others again were feebly united to the 

 rock, especially at one end of the prisms and these hung down- 

 ward in large groups. No radial or other regular grouping of the 

 crystals was observed. The specimens are quite free from other 

 minerals, the conditions, at the time of formation of the crystals, 

 seeming to have been just right for pisanite and not right for any 

 other mineral. 



The mineral probably crystallized out from a solution of iron 

 and copper sulphates. Zonal structure, though common in the 

 artificial crystals, was not observed in the natural ones. 

 Inclusions of pyrite are not uncommon and drusy pyrite fre- 

 quently covers the crystals to a large extent. 



CrystallograpMc Characters . — The crystals average about 

 5 mm. in length and about 1 mm. in thickness. Many are 

 much longer and the thickest one measured 3 mm. by 4 mm. on 

 the base. Certain crystals of pisanite had been partially dis- 

 solved, the re-solution going on with a remarkable difference in 



* Inorganic Chemistry, by Ira Rem sen, 5th edition, 1898. pp, 218, 709. 



OS 



PISANITE. 



