LEONHAUD MILLERITE IN ST. I.OUIS. 495 



perforates it, sometimes goin-^- through the centres of opposite 

 faces, but mostly without regard to symmetry. 



The composition of the Millerite in St. Louis, as shown by an 

 analysis of C. Luedeking, of Washington University, and several 

 determinations made by myself, varies not much from the theo- 

 retical composition of Nickelsulphide, viz., 64.45 p. ct. of Nickel 

 ^"^^ 35-55 P- ct. of Sulphur. The only admixture is Iron, the 

 amount of which varies from o.S p. ct. in some needle-like crys- 

 tals to 2.65 p. ct. in some of the spear-like forms. 



The specific gravity of the Millerite — average of many determ- 

 inations — is 5.038. 



The annexed Plates show different forms of Millerite in their 

 natural size. They are printed from photographic views by the 

 artotype process, in the establishment of R. Bennecke. The upper 

 figure Plate I. shows a Calcite crystal nicely developed on both 

 ends, pierced by a spear of Millerite. Besides, the crystal en- 

 closes a very large number of straight needles of Millerite which 

 can be plainly seen in the crystal, and are indicated on the figure 

 by faint, nearly horizontal, lines. The specimen is quite unique, 

 and is in possession of Dr. Hambach. The lower figure shows 

 a cavity in the limestone. On the left side rises a tuft of straight 

 needle-like crystals of Millerite, and on the right side a thick stem 

 of it. This " spear," before broken, was attached with both ends 

 to the walls of the cavity, and both ends are surrounded by thick 

 bunches of the same mineral. 



On Plate II. the upper figure represents a group of Calcite 

 crystals. The middle part of each crystal is of dark, nearly black, 

 color, caused by minute particles, probably of Millerite, while 

 both ends of the crystal are white. On the Calcite crystals are 

 deposited small flakes of Barite. The lower figure shows the 

 interior of a cavity lined with pink-colored Dolomite crystals, 

 filled with irregular bunches of thin, thread-like Millerite. 



The originals of the last three figures are in the collection of 

 Washington University, St. Louis. 



