CROCIDOLITE. 



Crocidolite. Occurs both compact and 

 in long and easily separable fibres, which 

 are flexible and elastic, like those of Asbestos. 

 Colour and streak lavender-blue and leek- 

 green. Lustre sillvv. Opaque. H. 4. S.G.3-2. 



Comp. (Na, Mg) 2Si + 3(Fe, 'fcj'i) + 5H. 



Anah/sis by Stromeyer : 



Silica 51-64 



Protoxide of iron . . . 34-38 

 Soda . . ... . 7-11 



Lime 0-05 



Magnesia .... 2-64 

 Peroxide of manganese . 002 

 Water 4-01 



99-85 

 BB at a strong red heat, even in the flame 

 of a spirit-lamp, fuses to a black, swollen, 

 strongly magnetic glass. With borax forms 

 a transparent green glass. 



Localities. The Grigna country, beyond 

 the Great Orange River, in South Africa, 

 •with Magnetite, Stavarn, in Norway, in 

 Zircon-syenite. Greenland. Golling, in Salz- 

 burg, in Gypsum. 



Name. From xioy,);, wool, in allusion to its 

 ivoollv, fibrous structure. 



Brit Mus., Case 34. 



Crocoisk, Beudunt; Crocoisite, v. Ko- 

 hell. Oblique : primary or cleavage form an 

 oblique rhombic prism. Occurs in very dis- 

 tinct crystals ; also massive. Colour various 

 tints of hyacinth-red. Translucent, with 

 strong refracting j)0wer and adamantine lus- 

 tre. Streak orange-yellow. H. 2'5 to 3. 

 S.G. 0-9 to 61. 



Fig 136. 



Comp. Monochromate of lead, or Pb Cr = 

 oxide of lead, 68*7, chromic acid 313 = 

 100 0. 



Analysis bv Berzelius : 



Oxide of lead. . . . 68-5 

 Chromic acid . . . .31-5 



100-0 

 BB decrepitates when heated, assuming for 

 the time a darker colour; but it may be 

 fused to a black shining slag, containing 

 globules of metallic lead. Colours glass of 

 borax green. 



CROMFORDITE. 99 



Soluble in nitric acid, forming a yellow 

 solution. 



Localities. In narrow veins, traversing 

 decomposed gneiss, at Nischne Tagilsk, near 

 Beresow, in Siberia ; and in fine crystals in 

 decomposed granite at Conghonas do Campo, 

 in the Brazils. Rezbanya, in Hungary. 

 The Bannat. Luzon, one of the Philippine 

 Islands. 



Crocoisite is used as a pigment, but the 

 colour is not permanent. 



Name. From x^oxom^ aurora-yellow. 



Brit. Mus., Case 39. 



M. P. G. Principal Floor, Wall-case 21. 



Croisette. See Staurotide. 



Cromfordite, Greg 8f Letfsom, Pyrami- 

 dal. Primary form a rectangular four- sided 

 prism ; in which it also occurs either perfect, 

 or having the lateral and also the terminal 

 edges replaced. Colour white, greyish or 

 yell w. Transparent or translucent. Streak 

 snow-white. Rather sectile, and easily 

 frangible. Fracture conchoidal, with a splen- 

 dent adamantine lustre. H. 2-75 to 3. S.G. 6 

 to 6-3. 



Fig. 137. 



Comp. Chlorocarbonate of lead, or Pb 



CI -t- Pb C = chloride of lead 51, carbonate 



of lead 49 =-100. 



Analysis, by Klaproth, recalculated by 



Berzelius : 



Oxide of lead . . .85-5 



Muriatic acid . . . 14-0 



Carbonic acid . . .6-0 



105-5 

 BB melts readily in the outer flame to a 

 yellow globule, which on cooling becomes 

 white, and somewhat crystalline ; on char- 

 coal yields a globule of lead. 



Soluble with effervescence in nitric acid. 

 Localities. The finest crystals of this 

 rare mineral were obtained many years ago, 

 in the air-shaft of a mine between Cromford 

 and Wirksworth, in Derbyshire; many of 

 these specimens are deposited in case 57 B, 

 at the British Museum. It has lately been 

 found by Mr. Brice Wright, in minute 

 cr}'stals, at Lossiemouth lead-mine, at Elgin> 

 in" Scotland, and has also been met with at 

 Huel Confidence, in Cornwall. 

 h2 



