98 Moses — Mineralogical Notes. 



Art. X. — Mineralogical Notes ; by A. J. Moses. 



(1) Mercuric Iodide from New South Wales. 



Mr. Roy Hopping submitted to me for examination a small 

 specimen of impure limonite from the Broken Hill Mines, 

 which was coated upon one side with a thin layer of bright 

 scarlet or minimum red color. Under the microscope this 

 layer proved to be made up of little sharp-edged cubes about 

 l/10 mm on an edge and with slightly etched or roughened 

 faces. 



The only measurements possible were with the cross hairs. 

 Any face brought squarely beneath the objective was either 

 square or rectangular, or in a few observed instances not less 

 than three and probably all four of the corners were replaced 

 by lines equally inclined to the sides, that is corresponding to 

 planes of the octahedron. Other faces showed linear markings 

 parallel to both diagonals. Geometrically everything suggested 

 the hexoctahedral class of the isometric system. No confirma- 

 tion could be obtained with polarized light because of surface 

 irregularities, while in an attempt to mount for grinding 

 smooth the crystals became yellow and disappeared. 



The following tests were made as to composition : A group 

 of three or four crystals on a small mass of gangue was heated 

 on a glass slide and watched, during the heating, through a 

 hand glass. The crystals slowly and apparently completely 

 volatilized without any visible change of color, and in a similar 

 test in a narrow closed tube there was obtained a sublimate in 

 part yellow but principally of the original bright red color, 

 composed however of crystals which were rather need.le-like 

 than cubic. Two or three crystals placed on white paper and 

 touched with a hot bead gave a sublimate corresponding ex- 

 actly to the red and yellow sublimate of the iodides of mercury 

 which is obtained by heating a mercury compound on a plaster 

 tablet with bismuth flux. 



To further check the presence of mercury, Mr. J. S. McCord 

 made for me Behren's microchemical test for mercury, by first 

 subliming two or three particles on a glass slide, dissolving in 

 aqua regia, evaporating to dryness, and then adding to the dry 

 substance a minute drop of each of ammonic sulphocyanide and 

 cobalt nitrate, obtaining immediately the fine groups of blue 

 diverging needles of Co(CyS 2 ), Hg(CySJ. A parallel test was 

 made with artificial mercuric iodide, and throughout the beha- 

 vior was the same. The deep green flame of copper iodide was 

 obtained when a salt of phosphorus bead saturated with copper 

 oxide was touched to a crystal of the substance and again heated. 



