B. J. Harrington— Pyrrhotite from EUzahethtown. S87 



the pyramid 1, by which the vertical axes of the two indi- 

 viduals are brought nearly at right angles to each other, since 

 0/\ 1 = 135° 8'. This combination of three individual crystals 

 is analogous to the penetration -twins of staurolite, described 



Dr. Harrington has kindly furnished some notes upon the 

 occurrence and chemical composition of this pyrrhotite, which 

 he allows me to append here. 



The deposit from which the crystal of pyrrhotite was ob- 

 ained is economically important as being the source from 

 /hich considerable quantities of pyrite have been derived for 

 he manufacture of sulphuric acid. It occurs on the nine- 

 eenth lot of the second concession of Elizabeth town, Ontario, 

 n rocks belonging to the Laurentian system, but its true char- 

 cter has not yet been ascertained. To the mineralogist it is 

 especially interesting on account of the association of minerals 

 which it affords. The minerals number a dozen, and proba- 

 pecies, being pyrite, pyrrhotite, magnetite, quartz, 



bly 



Of these the pyrite and calcite occur in greatest abundance. 

 The former is generally massive, but is sometimes well crystal- 

 lized — the most common form being a combination of the cube 

 and octahedron. Perfect octahedrons with the axes more than 

 two inches in length have been obtained, and mammillary 

 groupings of cubical crystals with rounded faces occasionally 

 occur. According to the determinations of Hunt and Macfar- 

 lane (Geol. of Can., 1863, p. 606, and Can. Nat., 1st Ser., vol. 

 vii, p. 194) the pyrite contains about half a per cent of oxide 

 of cobalt. 



Calcite forms the principal gangue in which the other mine- 

 rals are embedded. It is mostly massive, but is also found on 

 the walls of cavities in the form of obtuse rhorabohedral crys- 

 tals, often curiously modified. It ranges from opaque to trans- 

 parent, and varies much in color, being white, gray, fawn- 

 colored and sometimes red. The compact black mineral 

 alluded to above also frequently forms the gangue of tbe pyrites 

 and with it is occasionally associated a triclinic feldspar (^proba- 

 bly labradorite) showing a beautiful play of colore. Magnetite 

 is rather common and sometimes occurs in the form of small 

 irregular grains scattered through the calcite. The mineral 

 which I take to be cacoxenite — the occurrence of which in 



