BY W. F. PETTERD, C.M.Z.S. 63 



102. Deweylite f Hydrous Basic Silicate of Magnesium), 



This is an amorphous, greasy, smooth, and translucent 

 substance, which in colour affects the paler shades of yel- 

 low, brown, and bluish. It is brittle and commonly much 

 fractured, and at times it appears as if in layers. It con- 

 tains more water than serpentine, of which it appears to be 

 an alteration product. It occurs in rather narrow seams, 

 at times reaching to as much as a foot in width, traversing 

 a,nd closely connected with serpentine. 



Locality : Harmon's Rivulet, near Parson's Hood 

 Mountain. It also occurs in the vicinity of Nort-li Mt. 

 Heemskirk. 



1('3. DiALLAGE f Silicate of Calcium and Magnesium). 



A rock-forming pyroxene, which occurs in various shades 

 of green, grey, and brown. Its lustre is vitreous and occa- 

 sionally rather pearly. It forms extensive ultra-basic 

 masses on the west side of the Heazlewood River, and in 

 the vicinity of the Hampshire Hills ; also as a constituent 

 of the gabbroid rocks at the Whyt)e River, Mt. Agnew, and 

 -at Dundas. 



104. DiALOGiTE (Carbonate of Manganese). (See Rhodo- 



CHROSITE.) 



105. Diamond (Pure Carbon). 



It is beyond doubt that several veritable diamonds have 

 been discovered in this island at a locality on a small tribu- 

 tary of the Pieman River, and at Harvey's Creek, which 

 falls into the Savage River and also flows into the Pieman. 

 They were obtained in alluvial drift with a little gold. All 

 the specimens obtained showed good crystallisation, of the 

 prevalent octahedral form, with the characteristic rounded 

 facets. They presented a remarkable uniformity as to size, 

 nearly all being about J-carat in weight, although one 

 reached J-carat, and all have one exact tinge of yellow, 

 although one or two had a tendency to be paler at the 

 apices of the crystals. They were obtained in shallow 

 alluvial and quartz grit and clay, and did not show any 

 appreciable amount of attrition. The total number found 

 which can be satisfactorily authenticated does not exceed 

 sixteen, or at the outside eighteen. Altogether not less 

 than seven have passed through the writer's hands. When 

 several were tested by being placed within the influence of 

 a tube containing radium bromide of 1,000,000 strength, 



