168 Decomj^osition of Iron Pyrites. 



veinstone are colored by a film of reddish to reddish brown iron- 

 ochre. 



No. 3. Pyrr. otite. Elizabeth town, Ontario, Canada. A tab- 

 ular mass, a])pareutly a fragment of an imperfect crystal imbed- 

 ded in calcite. Fresh fracture, gray, glistening with high lus- 

 tre, and uneven. Strongly magnetic. Small geodcs in/the 

 vicinity are studded with minute crystals, brilliant bronze- 

 colored, hexagonal, with many modification-planes. Decompo- 

 sition : dull reddish bronze-colored tarnish, iridescent in places. 



Pyrrhotite. 



o p . Weight Evidences of ten- 

 No. Locality. tiro ^y taken, in dency to decom- 



at 10 o. • ; • 



grains. position, 



1 Ore Knob, N. C. 4.661 8.119 Iridescence. 



2 Schneeberg, Tyrol. 4.596 2.298 Tarnish and ochre- 



ons film. 



3 Elizabethtown, Can. 4.542 1.039 Dull tarnish. 



In No. 1, the density is undoubtedly increased by the inter- 

 mixture of a small proportion of pyrite throughout the massive 

 ore. In No. 3, the figures are lower than those obtained by both 

 Smith and Harrington (Nos. 4 and 12 of Table in Part I, of this 

 paper, page 371). The determination in No. 2 was made with 

 the utmost care, by scraping the shining crystals from a choice 

 specimen, digesting them repeatedly in a weak solution of tar- 

 taric acid to remove adhering iron-oxide, and then picking out 

 the pure crystals under a loup. The specific gravity obtained 

 agrees exactly with the average, 4.597, of the sixteen best deter- 

 minations already published (Part I, page 372), and this figure, 

 (or 4.6, as already suggested by Rammelsberg), probably approx- 

 imates very closely to the density of normal pyrrhotite. 



In this connection it may be added, in regard to troilite, that its 

 superior specific gravity, 4.681 — 4.817, which Rammelsberg has 

 discussed^ with reference to tlie constitution of pyrrhotite, ap- 

 pears to be connected with two conditions: the intense sur- 

 rounding compression, which has attended the solidification of 

 the meteorite and its strong crystallization, (indicated by the 

 Widmannstattian figures), during cooling from the state of fu- 

 sion ; and also, it may be, the enclosure of microscopic films and 



1 Zeits. d. d. geol. Gesells., (1864), XVI, 271. 



