15(5 Smyth, Jr. — JVeto Locality of Pyrrhotite Crystals 



Art. XV. — A JVeio Locality of Pyrrhotite Crystals and 

 their Pseudomorphs y by C. H. Smyth, Jr. 



The rebuilding of the old " Seneca Turnpike" through Cen- 

 fcral New York, during the summer of 1907, led to consider- 

 able opening up of new and old quarries along the line of the 

 highway. Among these, is a small quarry in Clinton rocks, 

 whose location is clearly marked on the Oriskany Sheet of the 

 U. S. Geological Survey, being at the point where a small 

 stream crosses the highway about half-a-mile east of Lairds- 

 ville. 



"While searching the quarry for celestite and strontianite, 

 which occur here in small quantity, the writer found a small 

 rusty-brown hexagonal crystal which, on being touched, went 

 to pieces along basal cleavage or parting planes. Without a 

 magnifier, the mineral looked much like weathered mica, but 

 the geological conditions precluded the possibility of such being 

 the case. Further search was rewarded by the finding of a 

 number of crystals in much better condition, and it was 

 apparent that the mineral was pyrrhotite. 



The crystals range in size from microscopic up to about 5 mm 

 in greatest diameter, and while some of them have the normal 

 bronze-yellow color of pyrrhotite, they are more commonly 

 tarnished or superficially altered to limonite, and range from 

 yellowish brown to black in color, often with strong iridescence. 



The crystals are, for the most part, exceedingly simple, con- 

 sisting of the prism and base, with no other faces developed, 

 but they show three rather distinct habits. The most common 

 of these is prismatic, the length of the prism being three or 

 four times the diameter of the base. Some of these crystals 

 are tapering and probably have the form described by Dana,* 

 or one closely related, but the faces are too imperfect to per- 

 mit a determination. Another habit, shown by the largest 

 crystals found, is tabular parallel to the base, thus being of the 

 type most common for this species. In this type, the basal 

 diameter is from two to six times the length of the prism. In 

 both of the foregoing types the prism faces are deeply striated 

 parallel to the base. 



Finally, the pyrrhotite is scattered over the surfaces of 

 associated minerals in minute, very thin scales, looking almost 

 like dust, but when magnified showing the normal hexagonal 

 shape, and thus constituting an extreme case of tabular habit, 

 resembling micaceous hematite. Many of these minute scales 

 are of irregular shape and sometimes are in arborescent groups. 

 There are no differences of association, age or condition of 

 *Dana, E. S., this Journal, xi, p. 386, 1876. 



