J. M. Davison — Internal Structure of Cliftonite. 467 



Art. XLI. — Internal Structure of Cliftonite;* by John 



M. Davison. 



Graphite crystallized in the isometric system was first 

 found by Haidinger in the Arva meteoric iron ; afterwards by 

 Fletcher in the Youndegin and Cocke Co. irons and was 

 named by him cliftonite. Huntington afterwards found it in 

 the Smith ville iron. 



Fletcher thought these crystals were pseudomorphs after 

 pyrite. Rose and Brezina hold that they have been altered 

 from diamond to graphite. 



In dissolving a troilite nodule from the Smithville iron the 

 writer found a number of these crystals. Some were loose in 

 the residue from the aqua-regia solution, and all of these were 

 cubo-octahedral in form, the planes of each being equally 

 developed. The crystals were from 0-13 mm to 0*23 mm in diam- 

 eter. Other crystals of about the same size were attached to 

 larger pieces of uncrystallized graphite, seemingly in form of a 

 curving string of compressed cubes or plates. On two of these 

 plates angles of 120° and 104° could be roughly measured. 

 Other angles seemed to be 90°. 



To see whether the cliftonite crystals occurred also in the 

 kamacite and tsenite a piece of the Smithville iron of about 

 the size of the troilite nodule was dissolved. In the insoluble 

 residue fragments of graphite and a single hexagonal plate of 

 graphite were found but not one of the cliftonite crystals. 



Four of the cubo-octahedrons were mounted in Canada bal- 

 sam and carefully ground with a fine hone. The grinding 

 was parallel to a face of the cnbe. On each, as the cube face 

 enlarged, a square appeared lying w T ithin, its sides parallel to 

 the planes of the octahedron and turned 45° from the edges of 

 the cube. As the grinding went on this square enlarged to a 

 maximum and then decreased, thus showing that the embed- 

 ded form was not a cube but an octahedron which was being 

 ground normal to a solid angle. 



Measurements on two of the crystals gave these successive 

 sizes of the squares : 



Cliftonite crystal 0-23 mm X 0'24 ram Cliftonite crystal 0*15 



inner square # 04 inner square 0*07 



" " 0-08 " " 0-06 



u u q. 10 u u q. 05 



U Q . 06 u u . 04 



" " 0-03 



mm 



Read before the Rochester Academy of Science, April 14, 1902. 



