DIAMOND SPAR. 

 Diamonds appear to occur generally in 

 countries where there is a laminated rock 

 called Itacolumite. They are procured by 

 washing, either from the soil or from super- 

 ficial deposits. At Minas Geraes in the 

 Brazils, there are two of these Diamond- 

 bearing deposits ; the one a gravel composed 

 of broken fragments of Quartz covered with 

 a thin layer of sand or earth — Avhich is 

 called gurqulho, the other called cascalho, 

 (See 31. F. G. Horse- shoe Case, No. 1) 

 made up of rolled pebbles of Quartz in a 

 base cf ferruginous clays— the Avhole, as 

 well as the talcose clay on which it rests, 

 being the debris of 'talcose rocks. The 

 finest Diamonds are found in the gurgulho. 



There are also mines called Bagugem in 

 the province of Aiinas Geraes, on the banks 

 of the river Patrocinho, which have pro- 

 duced some large stones : one in 1851 weigh- 

 ing 117 carats, and another more recently 

 of 247^ carats. 



The most celebrated mines are situated to 

 the north of Eio Janeiro, on the rivers 

 Jequetinhonha and Pardo : it has lately, also, 

 been found in Bahia, at the mines of Surua 

 and Cincora on the river Cachoeira, but the 

 quality of the Cincora Diamonds is inferior 

 to those of Minas Geraes or Cuyaba. 



The Uralian Diamonds occur in the de- 

 tritus along the Adolfskoi rivulet, where it 

 is worked for Gold, and also at other places. 

 A few Diamonds have also been found in 

 Georgia and N. Carolina, also in Kutherford 

 CO., N. C , and Hull co. Ga., in the United 

 States ; in Australia, on the banks of the 

 Turon ; at Pontiana in Borneo, on the west 

 side of the Ratoos mountain, and on the 

 river Gunil in the province of Constantine 

 in Algiers. 



Brit. Mus., Case 4. 

 M.F.G. Horse-shoe Case, Nos. 1 to 9. 

 Case 11. (The first diamond brought to 

 this country from Australia.) 



Diamond Spak. See Corundum. 

 DiANiUM. Anew metallic acid, belonging 

 to the same group with tantalic and niobic 

 acids, discovered by Von Kobellin Euxenite, 

 ^Eschyiiite, Samarskite, and in a Tantaliie 

 from Tammela. It also exists, though in a 

 less pure state, in the Tantalite of Greenland, 

 in the Pyrochlore of the Ilmengebirge, and in 

 the brown Wohlerite. 



The Tantalite from Tammela, which Von 

 Kobell calls Dianite, has a dark, brownish- 

 red streak and a specific gravity of 5*5, while 

 other Tantalites vary in density from 7-06 

 to 7-3, and have a dark grey streak. 



Titanic acid is easily distinguished from 



DIASPORE. 113 



other acids of the same group, by boiling 

 it with muriatic acid and tin, and diluting 

 the solution with water. The blue colour 

 then passes to rose red, and the solution re- 

 tains this colour several days. When. 

 Dianic acid is present, the blue colour pre- 

 dominates, but, after standing some hours, 

 the rose colour of Titanic acid appears. 



BB Dianic acid behaves like the Tantalite 

 of Kimito. 



DiAPHORiTE. See Allagite. 

 DiASPORE, Hairy, Philips, Nicol. Rhom- 

 bic : usually crystallized in thin flattened 

 prisms, sometimes acicular. Also occurs 

 massive, in slightly curved lamina^ which 

 may be easily separated, of a greenish-grey 

 colour, with a shining pearly lu.stre : also in 

 cellular masses, with a pearlj^ lustre, inter- 

 cepting each other in all directions, and of a 

 brown hue externally, but perfectly colour- 

 less and transparent when reduced to thin 

 laminae. Verv brittle. Scratches glass. 

 H. 6-5 to 7. S.G. 3-43. 



Vl 



Fig. 165. 



Comp. Hydrate of alumina, or Al H=alU'» 

 mina 851, water 14-9 -=100-0. 



Analysis from Siberia by Dufrenoy : 



Alumina 



. 74 66 



Water .... 



. 14-58 



Peroxide of iron . 



. 4-51 



Silica 



. 2 90 



Lime and magnesia 



. 1-64 



98-29 



Heated in a glass tube decrepitates vio- 

 lentl}^ and crumbles into small, white, bril- 

 liant scales, which evolve water when more 

 strongly heated. 



BB infusible, alone. 



Not soluble in boiling muriatic acid, which 

 only extracts the oxide of iron mechanicalh-- 

 mixed with it. 



Localities. Near Kosoibrod, district of 

 Katherinenburg, in the Ural. Schemnitz. 

 Broddbo, near Pahlun, in Sweden. St. Gott- 

 hard, in dolomite. The Grecian archipelago, 

 with Emery. 



Name. From hieia-yni^u^ to disperse ; from 

 decrepitating and being dispersed when 

 placed in the flame of a candle or BB. 



Diaspore may be distinguished from Kya- 

 nite, to some varieties of which it bears a 

 close resemblance, by its superior lustre. 



