388 TRIPOKLAS. 



inner flame, yields a large quantity of phos- 

 phide of iron. 



Easily solul>le in muriatic acid. 



Localities. Near Limoges, in France, 

 associated with Apatite, in a quartz-vein 

 traversing large-grained granite. Peilau, 

 in Silesia (H. 4. S. G. 3-617), frequently 

 coated with Oxide of Manganese. 



Name. From TPtTrXoo?, three-fold, in allu- 

 sion to its tliree component parts, and the 

 cleavage in three different directions. 



Brit. Mus., Case 57. 



Triploklas, Breithaupt. See Thom- 



SOIiriTE. 



Tripoli, Jameson, Kirwan, Phillips. A 

 variety of earthy silica, or a fine arenaceous 

 variety of Quartz mixed with clay. It 

 occurs massive with a coarse, dull, earthy 

 fracture, is meagre and rough to the touch, 

 and yields to the nail. Colour various 

 shades of grev, yellow and red. Opaque. 

 Soft and friable. S.G. 1-86 to 2 2. 



It is found in veins in Tripoli, in Africa, 

 (whence it was first brought and derived 

 its name) ; at Arnberg, in Bohemia, near 

 Prague ; in Saxony, Thuringia, Tuscany, the 

 Puy de Dome in France, and near a stream 

 seven leagues from Menat in Auvergne ; 

 Corfu, &c. Near Bakewell in Derbyshire, in 

 upper Mountain Limestone. 



Tripoli is used, when reduced to powder, 

 for polishing metals, marbles, the glasses of 

 optical instruments, and other hard sub- 

 stances. The Tripoli of Polinier, near 

 Pontpean, four leagues from Rennes, in Brit- 

 tany, is the most suited for lapidaries who 

 polish gems of the first order. That ap- 

 proximating in colour to a yellowish-white 

 should be preferred, because it is rarely 

 sandy. 



The Tripoli of Menat is produced from 

 shale, by the spontaneous combustion of 

 lignites. 



Trippel. See Tripoli. 



Tritomite, Dan% Weibye 8f Berlin. A 

 hydrous mineral related both in form and 

 composition to Helvine and Garnet. Cubical. 

 Tetrahedral. Cleavage indistinct. Colour 

 dull brown. Subtranslucent. Lustre sub- 

 metallic, vitreous. Streak dirty yellowish- 

 gi-ey. 



Comp. R Si + 2H. 





Analysis, by Berlin : 





Silica .... 



. 20-13 



Alumina 



. 2 24 



Peroxide of cerium 



. 40-36 



Peroxide of lanthanium 



. 15-11 



Yttria .... 



. 0-46 



Lime .... 



. 5-15 



TROXA. 

 Magnesia ... 

 Protoxide of iron 

 Soda .... 

 Manganese, copper, tin, wol- 



framium . 

 Loss by ignition . 



0-22 

 1-83 

 1-46 



4-62 

 7-86 



99-44 



BB yields water and affords a weak 

 fluorine reaction : with borax a glass which 

 is reddish' yellow when hot, but becomes 

 colourless when cold. 



In powder, gelatinises in muriatic acid, 

 with evolution of chlorine. 



Locality. The Island Lamo, near Bre- 

 vig, in Norway, in coarse syenite. 



Trombolite, Breithaupt. See Throm- 



BOLITE. ^ 



Trona, Dana, Dufrenoy, Hausmann, 

 Nicol, Phillips, Native Sesquicarbonate of 

 Soda. Oblique : primary form an oblique 

 rhombic prism. Seldom occu.rs distinctly 

 crystallized, but generally in fibrous masses 

 composed of a congeries of minute crystals. 

 Colour white, inclining to yellowish -grey 

 when impure. Lustre vitreous, glistening. 

 Transpaient when in minute crystals; in 

 large masses translucent. Streak white. 

 Taste pungent and alkaline. Rather brittle. 

 Fracture uneven. H. 2-5 to 3. S.G. 2-112. 



Fig. 442. 



It dissolves in water more readily than 

 the bicarbonate, but less so than the simple 

 salt (Natron), from which it is also dis- 

 tinguished by crystalline form, superior 

 hardness and specific gravity, and by not 

 being deliquescent. 



Comp. Sesquicarbonate of soda, or Na^ 



C3+3H = soda 37-8, carbonic acid 40-2, 



water 22-0 = 100. 



Analysis, by Klaproth: 



Carbonic acid . . . 38-0 



Soda 37-0 



Sulphate of soda . . .2-5 

 Water 22-5 



lUO-0 



Localities. Suckena, two days' journey 

 from Fezzan, in Africa. Barbary. Columbia. 

 (See Urao.) Maracaibo, South America. 

 Near the Sweetwater River, Rocky Moun- 

 tains, N.A. 



Brit. Mus., Case 41. 



