Geology and Mineralogy. 161 



6. On Harmotome from the vicinity of Port Arthur, On- 

 tario ; by W. F. Fekrier, (communicated by permission of the 

 Director of the Geol. Survey of Canada). — The specimen of 

 harmotome to be described was obtained in 1887 by Dr. A. C. 

 Lawson, in the Thunder Bay District, Lake Superior. In the 

 absence of Dr. Lawson, the precise locality is not known at 

 present, but it came from one of the mines in the immediate 

 vicinity of Rabbit Mountain (about 22 miles west-south-west of 

 Port Arthur), and, probably from the Rabbit Mountain Mine. 

 The crystallized minerals here fill vugs in true fissure veins 

 which cut the black argillites of the Animikie. On joining this 

 Department it devolved upon the writer to look over the speci- 

 mens collected by Dr. Lawson and it was in so doing that this 

 specimen was found. The form of the crystals first attracted 

 attention and qualitative tests proved that barium was present 

 in considerable quantity ; a further blow-pipe examination proved 

 that the mineral was harmotome. 



The crystals are double twins in which each individual is 

 twinned parallel to the base, and these two simple twins again 

 united in a double penetration-twin or fourling, with the clino- 

 dome as the twinning plane. These fourlings belong, as shown 

 by the striae on the crystal faces, to Streng's first type* in which 

 the simple twins are shortened in the direction of the vertical 

 axis. They are for the most part implanted on regular prisms of 

 calcite, terminated by the rhombohedron — \R, some of which 

 measure 4cm. in the direction of the vertical axis, and 8mm. in 

 that of the horizontal axis. The largest harmotome twin crystal 

 on the specimen was 4mm. long and 1mm. in width. The crystals 

 are white, and vary from subtransparent to translucent. The 

 faces are rough, but some of them show the characteristic stria- 

 tions with much perfection. 



Drusy quartz with an amethystine tinge of color forms the base 

 on which the calcite crystals are implanted, and purple fluorite is 

 also intimately associated with these minerals. Pyrite, in aggre- 

 gations and isolated cubes and octahedrons, is sprinkled over the 

 other minerals, and there is also present another sulphide, in 

 minute tufts of acicular crystals, which may be millerite, but the 

 material available was not sufficient for a satisfactory determina- 

 tion. The only other localities for harmotome in North America 

 which have come under the writer's notice are those of Sing 

 Sing in New York State, and the upper end of New York Island, 

 where it was found in seams in the gneiss at the excavations for 

 the 4th Avenue tunnel,f 1875. 



7. Long Island Sound in the Quaternary Era ; by J. D. 

 Dam. Erratum. — In the number of this Journal for December, 

 1890, page 436, line 22 from top, for eastward read westward, and 

 line 24 from top, for westward read eastward. 



Geol. Survey of Canada, Ottawa, Dec. 27th 1890. 



*See "Elemente der Mineralogie," Naumann-Zirkel, 12th Ed., p. 717, fig. 2. 

 fSee "Text Book of Mineralogy," E. S. Dana, pp. 346, 482, 1883. 



