37G TETRAHEDRAL COPPER. 



Tetrahedral Copper Glance, 3Iohs. 

 See Tetrahedrite. 

 Tetrahedral Garnet, See Helvine, 

 Tetrahedrite, Batia, Greg §• Lettsom. 

 Grey Copper or Fahlerz. Cubical. Occurs 

 crystallized in tetrahedrons; also massive 

 and disseminated. Cleavage imperfect, oc- 

 tahedral. Colour between steel-grey and 



Fig. 427. Fig 



iron- black. Opaque ; in thin splinters 

 cherry-red by transmitted light. Lustre 

 metallic. Streak like the colour, or inclin- 

 ing to brown. Rather brittle. Fracture 

 line-grained, uneven, or imperfect-conchoi- 

 dal. H. 3 Xp 4. S.G. 4-5 to 5-2. 



Comp. (-C-u, Ag, Fe, Zn) S + (Sb, As) S^. 

 Analysis, from Andreasberg, by C. Kuhle- 

 mann ; 



Sulphur .... 25-22 



Copper 37-18 



Antimony . . . . 27'38 



Zinc 5-00 



Iron 3 94 



Silver . . . . .1-58 

 Arsenic .... 0-67 



100-97 



BB gives off arsenical and antimonial 

 vapours; with borax affords the deep-green 

 reaction of iran; with soda, after much 

 roasting, yields a globule of metallic copper. 



When reduced to powder, it is decomposed 

 by nitric acid, affording a green solution. 



Localities. — English. Various Cornish 

 mines : Crinnis, Levant, Condurrow, Huel 

 Prosper {figs. 427 and 429), Herodsfoot, &c. 

 Combe Martin, Devonshire. — Scotch. Fass- 

 ney Burn, E. Lothian. Airthrie, in the 

 Ochil Hills. Mainland, Shetland?, at Sand- 

 lodge Mine. — Irish. Audley and Ardtulley, 

 and several other mines in Cork and Water- 

 ford. — Foreign. Andreasberg, in the Harz. 

 Kremnitz, in Hungary. Freiberg, in Saxony. 

 Kapnik, in Transylvania. Dillenburg, in 

 Nassau. 



Name. The name Tetrahedrite alludes 

 to the tetrahedral form of the crystals, in 

 which it ordinarily occurs. 



Brit. Mus., Case 12. 



31.* P. G. A 19, in Hall; mass of ore 

 with Iron Pyrites and Quartz, from Toman- 

 dashan copper mine. Loch Tay, Perthshire. 

 Principal Floor, Case 7 (Tuscany) ; Case 15 



THALITE. 

 (Cornwall) ; Wall-cases 7 and 28 (British) ; 

 16 and 17 (Foreign) ; with antimony and 

 silver, 16 (Spain). 



Some varieties of Tetrahedrite contain a 

 large proportion of silver, amounting some- 

 times to as much as 31 per cent. (JVeiss- 

 gilltigerz) ; others, especially those of North 

 Hungary and Schwatz, contain mercury, 

 up to 15 per cent. {Schwarzerz.^ 



A new variety of Tetrahedrite, from Ar- 

 dillats (Dept. du Rhone), in France, has 

 been described by Charles Mine, under the 

 name of Foumelite. It occurs with Galena 

 in a quartzose porphyry, and has a S.G. from 

 4-305 to 4 320. Its"^ composition calculated 

 from the mean of three analyses is, copper 

 o2-00, lead 12 00, sulphur 23-00, iron 3-00, 

 arsenic 8 00, antimony 22-00 = 100. 



Tetrahedrite is distinguished from Mag- 

 netic and Specular Oxides of Iron by its 

 total want of action on the magnetic needle ; 

 from Arsenical Iron by inferior hardness, 

 usually by its darker colour, and by not 

 yielding the odour of arsenic when struck. 



For varieties of Tetrahedrite, see Aph- 

 TONiTE, Fahlerz, Polytelite, Schwarz-. 

 ERz, Silberschwarzerz, Spaniolite. 



Tetraklasit, Hausmann. See Scapo- 



LITE. 



Tetraphyline. a variety of Triphyline, 

 from Keiti, in Finland. Is is of a yellow 

 colour when fresh broken, but becomes black 

 on exposure ; in other respects it resembles 

 Triphyline in outward aspect. It likewise 

 gives a stronger manganese reaction before 

 the blowpipe. 



Comp. 3(Li, Mg, Mn, Fe) P. 



Analysis., by Berzelius and Nordenskiold ; 

 Phosphoric acid . . . 42-6 

 Protoxide of iron . . . 38*6 

 Protoxide of manganese . 12-1 



Lithia 82 



Magnesia . . . . 1'7 



103-2 



BB with carbonate of soda on platinum 

 colours the flame red ; with boracic acid and 

 iron wire yields phosphide of iron. 



Texasite, Keiingott. A variety of Emerald 

 Nickel found on Chrome-Iron, in Serpentine; 

 at Texas, Lancaster co., Pennsylvania. 



Thalite, Owen. A kind of Saponite. 

 Does not occur crystallized, but diffused in 

 the amygdaloidal trap rocks of Lake Su- 

 perior. Colour pale yellowish-green, of the 

 consistence and hardness of wax. S.G. 

 2-548. 



BB tinges the outer flame slightly green ; 

 in thin splinters fuses at the edges. 



