502 Hewett and Shannon — Orientite, a neiv 



tion of chlorine and separation of flocculent silica. It is 

 practically insoluble in concentrated nitric acid but is 

 partly decomposed by boiling with moderately concen- 

 trated sulphuric acid and yields a rose-purple solution 

 which becomes brown on dilution, precipitating brown 

 manganic hydroxide. 



Material for analysis was selected with extreme care 

 as it was necessary to avoid, so far as possible, included 

 calcite and manganese oxides and also those portions of 

 the drusy crusts which bore superficial coatings of oxides 

 or of the colorless transparent opaline material. The 

 best specimens consisted of cellular masses made up of 

 thin ribs coated on both sides with drusy crystals. Such 

 masses were crushed and the purest grains and aggre- 

 gates of crystals were selected by hand under a high- 

 power binocular microscope. In many cases the thicker 

 ribs have a medial line of gray oxide and the groups of 

 crystals are often grown around a nucleus of opaque steel- 

 gray oxide as shown in the photomicrograph (fig. 1). 

 It was possible to recognize these areas of oxide under 

 the binocular microscope and to avoid them. The selected 

 samples were ground for analysis but, when examined 

 optically, they presented a rather unsatisfactory appear- 

 ance as many of the grains were more or less dusted with 

 what apiDeared to be a black opaque pigment of oxide. 

 The dark material appears to be an exceedingly fine dust 

 and many of the clear brown crystals have a central 

 nucleus of the dust-like material, the opaque core locally 

 having exactly the same form as the exterior of the 

 crystal. The samples on which the analyses given in 

 columns 1 and 2 below were made contained more or less 

 of this opaque material in from 10 to 20 per cent of the 

 grains. As treatment with heavy solutions and with an 

 electromagnet failed to effect any further purification of 

 the mineral, the muddy and the transparent grains have 

 practically identical specific gravity and magnetic attrac- 

 tibility. During microscopic examination of sample 2 it 

 was noted that the muddy impurity was practically 

 confined to the larger grains while the smaller grains were 

 mostly clear and transparent. Accordingly the finer 

 material was separated by livigation with water and the 

 product thus obtained showed very little of the opaque 

 impurity. An analysis- of this last portion is given in 

 column 3 below. As will be seen, the analyses show but 



