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138 TE1HTBIDES. ac 90° o' ad 90 0 ma 45 0 ec 61 23 TC 68 66 re 41 17 ee 76 46 rd 82 34 Combinations. Cleavage. C, '\ cma, crs. Opaque, same. In Lustre metallic, thin leaves very 1-8. G = 7'0 ... 7'2. „ „ Streak the flexible. Very sectile. h = ro ... „ , In the open tube emits a dense vapour and sulphurous acid, deposits a grey fusible sublimate of tellurate of oxide of lead close to the assay, and a white sublimate of tellurous acid at a greater distance. Before the blowpipe on charcoal melts easily, emits fumes, and deposits upon the charcoal a yellow sublimate^ which disappears in the inner flame, imparting to it a blue colour. After long exposure to the flame, a malleable globule of gold is left. Soluble in nitric acid, with the exception of the gold. Analyses of nagyagite from Nagyag a by Klaproth, b by Brandes, c by Berthier:— a b C Lead . 64-0 66‘49 631 Gold 9'0 8-44 0-7 Silver 0-5 trace Copper . 1-8 1-14 l-o Tellurium . 322 31'96 130 Antimony — — 46 Sulphur . 3’0 3-07 11-7 Petz found in three varieties 8‘64, 7'8l, 8’48 per cent, of gold, and only slight traces of silver. In attached crystals, seldom; usually in lamellar masses, and disseminated. Is found in veins with sylvanite, gold, pyrite, blende, anti- momte, quartz, brown spar, at Nagyag and Offenbanya in Tran sylvania. 2G. TETRADYMITE.—Bomine ; Beudant. Rhomboe- dnscher Eutom-Glanz; Mohs. Tetradymit; llausmann, Ilai- dinger. Rhombohedral. 100,111 = 74 0 41', 0 111, r 100, « In, z 211 twin-face.