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210 SULPHIDES. o, imperfect. Fracture uneven. Opaque. Lustre metallic. Iron- black. Streak the same. Sectile. h = 2'5. G = 6082...6-218. Decrepitates when heated. In the open tube yields a white sublimate and a smell of sulphurous acid. Before the blowpipe on charcoal melts very easily, and deposits a sublimate of oxide of antimony upon the charcoal. With borax yields a bead of silver containing copper, and imparts a blueish-green colour to borax. Its reactions with acids are the same as those of pyrargyrite and bournonite. Ag 9 B, b denoting sb and As, and a portion of the Ag being replaced by ■£&.. Analyses of polybasite a from Gruarisamey, b from Schemnitz, c from Freiberg, all by H. Eose:— a b C Silver . . . 64'29 72-43 69-99 Copper . . 993 3-04 4-11 Iron . . . 0'06 033 0-29 Zinc . . . — 0-69 - Arsenic . . 374 6-23 1-17 Antimony . 5-09 0-25 8 4 39 Sulphur . . . 17-04 16-83 16-35 In thin tabular crystals, massive and disseminated. Is found in veins in crystalline slate and transition rocks, and trachyte, with stephanite, pyrargyrite, blende, towanite, pyrito, quartz, calcite, in several mines near Freiberg in Saxony, Joa- chimsthal in Bohemia, Schemnitz in Hungary, Guanaxuato and Guarisamey in the province of Durango in Mexico. 98. STEPHANITE.—Brittle sulphuret of silver; Phillips. Argent antimonie sulfure noir ; Hauy. Prismatischer Melan- Glanz ; Mohs. Sprodglaserz; Hausmanu. Steplmuit; Hai- dinger. Prismatic. Oil,010=42° 32'-6; 101,001=34° 26'; 110,100 = 57° 49'-6. a loo, b 010, c 001, e 101, d 201, m no, p ill, t 221, z 112. e truncates the edge cd. be 90° o' ec 34 26 dc 53 54 ac 90 o ma 57 50 ba 90 o me 32 46 pc 52 10 rc 68 46 me 90° o' za 73 15 zb 62 44 pa 65 38 pb 48 4 ra 60 15 rb 37 55 dd' 107 48 mm 64 21 FIG. 216. O'