46 BLEIYITRIOL. 



Bleivitriol. See Anglesite. 



Blende. Cubical, tetrahedral. Primary 

 form the rhombic dodecahedron. Occurs 

 crystallized and amorphous, in macles, and 

 massive, fibrous, and botr3'oidal. The forms 

 of its crystals are very numerous. Structure 

 perfectly lamellar, and mechanically divi- 

 sible with facility into the dodecahedron, oc- 

 tahedron, obtuse rhombohedron, acvite rhom- 

 bohedron, and irregular tetrahedron. Lustre 

 splendent to adamantine. Colour brown, 

 yellow, red, blackish-brown, rarely green ; 

 white or yellow when pure. Translucent 

 or opaque. Streak varying with the colour, 

 from white to reddish-brown. Yields to 

 the knife, is moderately brittle, and easily 

 frangible in the direction of the laminas. 

 H. 3-5 to 4. S. G. 3-9 to 4 2. 



Fig. 55 



Fig. 56, 



Coinp. Sulphide of zinc, or Zn S = sul- 

 phur 33, zinc 67 ==100; but part of the zinc 

 is often replaced by iron and cadmium. 



BB infusible both alone and with borax, 

 when strongly heated in the outer flame it 

 emits vapours of zinc, which coat the char- 

 coal. 



Soluble in nitric acid with the evolution 

 of sulphuretted hydrogen. 



This mineral (the^Black Jack or Mock 

 Ore of the English miners) is of very 

 frequent occurrence, being met with in 

 beds and veins accompanying most of the 

 ores of silver, lead, and copper. It was 

 divided by Werner into three subspecies. 

 Yellow Blende, Brown Blende, and Black 

 Blende, Of. these the brown was consid- 

 ered to be the most common, and of inter- 

 mediate age between the other subspecies, 

 of which the yellow is the newest. The 

 value of this ore has considerably increased 

 of late years, but formerly large heaps of 

 refuse were frequently formed in the Cornish 

 mines of the Blende extracted in working 

 for Copper and Tin ores. Although thus 

 looked upon in itself as a worthless sub- 

 stance, it was considered a favourable indica- 

 tion as regarded future prospects ; the saying 



BLUE ASBESTOS, 

 being that " Jack rode a good horse;" by 

 which was meant that a rich deposit of the 

 ore in request might be expected to occur 

 below it. 



Localities. — Evglish. In Cornwall at 

 mines near St, Agnes (Jigs. 54, 55, and 56") 

 Huel Crofty, Camborne; and white, mam- 

 millated, with a fibrous structure, at Huel 

 Unity and Fowey Consols. Alston, and 

 other places in Cumberland. — Scotch. Of the 

 form of fg. 54, with Galena, in the Edin- 

 burgh coal-fields. — Foreign. The black va- 

 rieties are found in Transylvania, Hungar}-, 

 and the Harz. Fine black and brown 

 crystals are met with at Sahla in Sweden, 

 Ratieborzitz, in Bohemia, and many Saxon 

 localities. 



Name. From the German blendena, b? il- 

 liant ; from blenden, to dazzle. 

 Brit. Mus., Case 5. 



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

 27 to 29 (British); 21 (Foreign). 



Blistered Copper-ore. The name given 

 in Cornwall to botryoidal and reniform 

 varieties of Copper Pyrites (Chalcopyrite). 

 It is found at Cook's Kitchen, Huel Basset, 

 &c. 



Bloodstone. A jaspery variety of Quart:', 

 of a deep green colour, interspersed with red 

 spots like drops of blood. On account of it:^ 

 beautiful colour and great hardness, it is 

 much used for seals, rings, and such other 

 ornaments as are commonly made of Agat j. 

 That which possesses the most translucency, 

 and has the most numerous red spots is the 

 most highly esteemed. 



In the middle ages, the red spots were sup- 

 posed to be the blood of Christ. 



Bloodstone is also made into burnishers. 

 It is found massive in Bucharia, Tartary, 

 Persia, Siberia; also in Upper Saxony, Ice- 

 land, and the Hebrides. 



The name Heliotrope (from '■'Mo;, the sun, 

 and T^cVw, to turn) was given to it because, 

 when immersed in a vessel of water, it was 

 said to make the image of the sun to appear 

 in it of the colour of blood. The Ethio- 

 pian Heliotrope especially produced this 

 phenomenon. " Out of the water the sun 

 is seen in it as in a mirror, the eclipses of 

 the sun become visible, and the moon is 

 beheld to pass under the great star." (Pliny.) 

 Brit. Mus., Case 23. 



31. P. G. Horse-shoe Case, Nos. 551, 652. 

 Bl«edite, a mineral occurring on Anhy- 

 drite at Ischl, and proved b}' analyses of Von 

 Hauer to be identical with Astrakanitc. 

 Colour, orange-3'ellow. Translucent. Com- 

 pact. S. G. 2-251. 

 Blue Asbestos. See Crocidolite. 



