TERRA DI SIENNA. 

 Terra di Sienna, T. H. Rowney. A 

 kind of Ochre, of a brownish-yellow colour, 

 ■which acquires a fine and rich chestnut 

 colour by ignition, in which state it is used 

 as a paint, under the name of burnt Sienna. 

 Adheres to the tongue, and absorbs much 

 water without appearing moist. Fracture 

 earthy and conchoidal. Easily scratched 

 with the nail. S.G. 3 -46. 



Comp. 4ta Si + 6H. 





Analysis, by T. H. Rowney ; 





Silica .... 



. 11-14 



Alumina 



. 9-47 



Peroxide of iron . 



. 65-35 



Lime .... 



. 0-53 



Magnesia . 



. 0-03 



Water .... 



. 13-00 



99-52 

 BB with borax and microcosmic salt 

 gives a transparent globule, with an iron 

 reaction. 



Not in the least degree attacked by con- 

 centrated muriatic acid. 

 . Locality. The neighbourhood of Sienna, 

 in Italy. 

 Terra Miraculosa Saxoni^. See Te- 



RATOLITE. 



Terre 1 FouLON. See Fuller's Earth. 



Terre a Porcelaine, Brochant. See 

 Kaolin. 



Terre de Lemnos. SeeLsMNiAN Earth. 



Terre d'Ombue, Ha'dy. See Umber. 



Terre Sigillee. See Lemnian Earth. 



Tesselite, Brewster. A cube-like variety 

 of Apophyllite which, wiien optically ex- 

 amined, exhibits a peculiar tesselated or 

 mosaic-like structure. 



Analysis, from Faroe, by Berzelius : 



Silica 52-38 



Lime 24-98 



Potash 5-37 



Hydrofluoric acid . . 0-64 

 Water 16-20 



99-57 



Localities. Near Talisker, in Skye, in fine 

 white and nearly opaque crystals, associ- 

 ated with Scolezite. Naalsoe, in the Faroe 

 Islands, with Mesole and Chabasie. 



Brit. Mus., Case 27. 



Tesseralkies, Breithaupt. See Skut- 

 terudite. 



Tetartin, Breithaupt. (From riTa^ro;, the 

 fourth part, because a fourth part only of a 

 certain group of faces occurs in the crystals. ) 

 gee Albite. 



TETRAHEDRAL BORACITE. 375 



Tetarto - prismatic Felspar, Mohs. 

 See Albite, 



Tetarto - prismatic Vitriol Salt. 

 Mohs. Sulphate of Copper. See Cyanosite. 



Tetradyjiite, Brooke §- Miller, Hai- 

 dinger, Hausmann. Rhombohedral ; pri- 

 mary form an acute rhombohedron. Gene- 

 rally occurs massive, with a foliated 

 structure; sometimes in tabular crystals, 

 with a very perfect basal cleavage. Colour 

 pale lead-grey, inclining to tin-white ; in- 

 ternally splendent and shining. Lustre me- 

 tallic. In thin laminae, flexible and slightly 

 elastic. Soils paper. Sectile. H. 1-5 to 2. 

 S.G. 7-2 to 8-44. 



Comp. Sulphotelluride of bismuth, or 

 2Bi Te3 + Bi S^^bismuth 59-66, tellurium 

 35-86, sulphur 4-48 = 100. 



Analyses, (a) from Schubkau, by TFehrle ; 

 (6) from Cumberland, by Rammelsberg : 



. («) (b) 

 Bismuth . . . 60-0' 84-33 

 Tellurium . . . 34-6 6-73 

 Sulj.hur . . .4-8 6-43 

 Selenium . . . trace — 



99-4 97-49 

 Analysis (6) gives the formula Bi* + Te 



+ S4. 



Heated in a glass tube, yields metallic 

 tellurium, which sublimes in drops. 



BB fuses readily, exhaling odours of sul- 

 phur and selenium ; burns with a bluish 

 flame, forms a yellow film, with a white 

 border on the charcoal, and leaves a shining 

 metallic globule, which, on cooling, becomes 

 covered with a reddish film. The reduced 

 metal is brittle, and has a granular fracture. 



Dissolves readily in nitric acid, deposit- 

 ing flakes of sulphur. 



Localities. — English. Brandy Gill, Car- 

 rock Fells, Cumberland, in foliated masses 

 in quartz rock. — Foreign. Hungary, at 

 Schubkau, near Sheninitz, in trachytic con- 

 glomerate, and Deutsch-Pilsen (Molybdan 

 silve?-). Tellemark, in Norway. Bastnaes, 

 in Sweden. San Jose, in Brazil (Bornite). 

 Tellurium Mine, Fluvanna co., Virginia, in 

 mica-slate; near Pioneer Mills, Cabarras 

 CO., North Carolina, &c. U. S. 



Name. From TsrjaSv/w-o?, ybwr/'oZc?, because 

 of the occurrence of quadruple crystals. 



Brit. Mus., Case 3. 



M. P. G. Principal Floor, Wall-case 13 

 (British). 



Tetraedrit, Haidinger, v. Kobell.^Grey 

 Copper. See Tetrahedrite. 



Tetrahedral Boracite, Mohs. See 



BORACITE. 



BB 4 



