BLACK CHALK, 

 and 52. Upper Gallery, Wall-case, 43. No. 

 154. 



Black Chalk. A kind of clay containing 

 a large amount of carbon. Colour black. 

 Opaque. Sectile. Soils the fingers and leaves 

 a mark on paper. Streak black and shining. 

 H. 1 to l-5„ S.G. 2-1 to 2-2. 



Becomes red or white in the fire. 



Black Chalk is found in England, France, 

 Portugal, Spain and Italy. 



The finer kinds are made into artists' 

 crayons, and used for drawing on paper. 



Blaok Cobalt Ochre, Allan, Jameson, 

 Kirwan. See Earthy Cobalt. 



Black Copper, Phillips, Black Oxide 

 OF Copper. An impure, earthy, black oxide 

 of copper, resulting from the decomposition 

 of other ores ; being mixed with more or 

 less sulphide of copper, Pyrites, and other 

 impurities. See Melaconite. 



M. P. G., Principal Floor, Wall-cases 1 

 (British) ; 15 (Foreign). 



Black Garnet; Black Garnet of 

 Frascati. See Melanite. 



Black Hematite. See Psilomelane. 



Black Iron Ore. See Psilomelane. 



Black Jack. The name for Blende 

 among English miners. 



Black Lead. See Graphite. 



Black Manganese-ore, Jameson. See 

 IIausmannite. 



Black Silicate of Manganese. See 

 Opsimose. 



Black Silver. See Stephanite. 



Black Sulphide of Silver. The name 

 given to an earthy form of Silver Glance 

 found in some of the Cornish mines. 



Black Tellurium, Phillips. SeeNAGVA- 

 gite. 



Black Wad. See Wad. 



Blakeite. The name given to octa- 

 hedral crystals, possibly of iron- alum (Co- 

 quimbite) from Coquimbo, analysed by J. 

 H. Blake. 



Analysis : 



Sulphuric acid . . . 41"37 

 Peroxide of iron . . . 26-79 

 Alumina . . . .1-05 

 Magnesia .... 0*30 



Silica 0-82 



Water 29-40 



99-73 



Blattererz, Blattertellur. See 

 JSTagyagite. 



Blatterkies. See Marcasite. 



Blatterzeolite, Werner. See Heu- 

 landite. 



Blattriger Stilbit, Hausmann. See 

 Heulanditk. 



BLEISCHWEIF. 



45 



Blau-Bleierz, Werner. See Galena. 

 Blaue Eisenerz, Werner. See Vivi- 

 anite. 



Blaueisenstein, Klaproth. See Croci- 



DOLITE. 



Blauspath, Werner. See Lazulite. 

 Bleicarbonat, Naumann. See Ceru- 



SITE. 



Bleierde, Werner. See Cerusite. 



Bleifahlerz. See Bournonite. 



Bleigelb, Hausmann. See Wul^enite. 



Bleiglanz. See Galena. 



Bleiglatte. See Plumbic Ochre. 



Bleigummi. See Plumbo-Kesinite. 



Bleilasur. See Linarite. 



Bleihornerz, Naumann, v. Leonhard. 

 See Cromfordite. 



Bleimolybdat. See Wulfenite. 



Bleinierr, Hausmann. Bleinierite, 

 Nicol. Amorphous, reniform, spheroidal ; 

 also earthy and incrusting. Structure often 

 curved lamellar. Colour white, g\'G.j, yel- 

 low, brown. Lustre resinous. Dull or earthy. 

 Opaque to translucent. Streak white, 

 greyish or yellowish. H. 4. S. G. 3-93 to 

 5-05. 



Comp. Antimoniate of lead. 



Analysis from Cornwall, by Dr. J. Percy. 

 Antimonious acid . . 47-36 

 Oxide of lead . . . 40-73 

 Water 11-91 



100-00 



BB on charcoal fuses to a metallic glo- 

 bule, gives out fumes of antimony, and 

 finally yields a bead of lead. 



This mineral is, probably, a mechanical 

 mixture of Lead and Antimony Ochres. It 

 occurs at Nertschinsk, in Siberia, where it 

 is supposed to result from the decomposition 

 of other ores of antimony. Also, in large 

 detached masses near the surface of the 

 ground, at Trevinnick mine, near Endellyon, 

 in Cornwall, with Jamesonite and Antimony 

 Ochre ; and is the result of the decomposi- 

 tion of the former mineral. 



M. P. G. Principal floor. Wall-case 20. 



Bleibiulm, a black, powdery, sulphide of 

 lead. 



Bleischeelat. See Scheeletine. 



Bleischimmer. See Jamesonite. 



Bleisulphotricarbonat, Rammels- 

 herg. See Leadhillite. 



Bleischweif. The name given by Wer- 

 ner to compact Galena, in contradistinction 

 to the crystalline and granular forms of that 

 mineral. It occurs in veins, and is gene- 

 rally accompanied by common Galena. When 

 that is the case, the Bleischweif always 

 forms the sides of the vein. 



