100 CRONSTEDTITE. 



Name. After that of the locality, Crom- 

 ford. 



The name Hornblei (Corneous Lead-ore) 

 was not given to this mineral by Karsten 

 in consequence of its resemblance in certain 

 external characters to Kerargyrite or Horn 

 Silver, but from its chemical composition. 



Cromfordite is principally distinguished 

 from Cerusite or white lead ore, by its colour, 

 crystallization, fracture, inferior hardness, 

 and less specific gravity. 



Brit. Mus., Case 57 B. 



Cronstedtite, Steinmann. Hexagonal. 

 Occurs in regular six-sided prisms, tapering 

 towards their summits, and generallv adher- 

 ing laterally ; also massive in opaque jet- 

 black fibres, haAdng a brilliant lustre. Streak 

 dark leek-green. Thin laminae, somewhat 

 elastic. H. 2-5. S.G. 3-35. 



Fig. 138. 



Comp. (Fe MgMn)6 Si + '#e2 Si + 6H, or 



more simply Fe^ ¥e Si + 3H = silica 17-68, 

 peroxide of iron 30*63, protoxide of iron 

 41-36, water 10-33 = 100. 



Analysis from Przibram, by Damour : 



Silica 21-39 



Peroxide of iron . . . 29-08 

 Protoxide of iron . . . 33-52 

 Magnesia .... 4*02 

 Protoxide of manganese . 1-01 

 Water 9-06 



98-78 

 5B froths a little, and in the reducing flame 

 fuses to a highly magnetic black slag ; with 

 borax gives an iron reaction. Wholly soluble 

 in salt of phosphorus: on the addition of a 

 little nitre gives an iron reaction, and a feeble 

 rose tint, indicating the presence of man- 

 ganese. 



In powder dissolves readily in dilute sul- 

 phuric or muriatic acid, forming a solution 

 which becomes gelatinous. 



Localities. English.— Hnei Maudlin, near 

 Lostwithiel, in Cornwall, on Fharmacoside- 

 rite and decomposed Pyrites. Foreign. — 

 Mines of Przibram, in Bohemia, in veins 

 containing silver ores; and associated with 

 Quartz and Magnetic Pyrites at the mines 

 of Conghonas do Campo, in the Brazils. 



CRYPTOLINE. 



Name. In honour of Cronstedt, the Swe- 

 dish mineralogist. 



Brit. Mus., Case 26. 



Cross-course Spar. The name given 

 to radiated Quartz by Cornish miners, from 

 its frequent occurrence in cross-courses. 



Cross- stone, Jameson. See Harmotome, 



Crow Coal. A kind of coal containing 

 only a very small quantity of Bitumen. It 

 is found at Alston Moor, in Cumberland. 



Crucite, La Metherie. See Chiastolite. 



Crumbling Felspar. See Albite. 



CKYOLirE, Phillips, J. W. Tayler. Mas- 

 sive. Structure lamellar. Colour white; 

 yellow or brown when associated with iron. 

 Lustre vitreous. Tnnslucent, becoming 

 transparent when immersed in water. Brit- 

 tle. H. 2-5 to 3. S.G. 2-96. 



Comp. Fluoride of aluminium and sodium, 



or 3Na F-f A12 F3 = aluminium 13-10, so- 

 dium 33-27, fluorine 53-63 = 100. 



Fuses below a red heat (in the flame of a 

 candle). 



SB on charcoal fuses to a globule, which, 

 is transparent while hot, but opaque on 

 cooling. 



Soluble in sulphuric acid with evolution of 

 fluorine. 



Locality. E vigtok, in W. Greenland,l 2 miles 

 from the Danish settlement of Arksut, form- 

 ing a vein in gneiss, about 80 feet thick and 

 300 feet long, running parallel Avith the 

 strata, in a direction nearlj' E. and W. 



Name. From ^-^vo?, ice, and a/^a?, stone, 

 because it melts like ice when held in the 

 flame of a candle. 



Probably the original colour of the mineral 

 was black or very dark, as the white Cryo- 

 lite only occurs at the surface, and bears 

 evidence of partial disintegration, becoming 

 more translucent and compact, and o^ a 

 darker colour in proportion to the de])th. 

 from the surface. The black Cryolite parts 

 with about 1 per cent, of acid and moisture 

 when heated to redness, and loses the whole 

 of its colour, and some of its transparency, 

 becoming perfectly white like the Cryolite 

 at the surface. 



Cryolite was first turned to account by 

 the Greeulanders in the manufacture of 

 snuff", xhey grind the tobacco-leaf between 

 two pieces of Cryolite, and the snuff so pre- 

 pared, which contains about half its weight of 

 cryolite powder, they prefer to any other. 



Brit. Mus , Case 58. 



M. P. G. Horse-shoe Case, No. 200. 



Ckyptoline. a fluid detected by Sir 

 David Brewster in minute cavities of Topaz, 



