118 DONACARGYRITE. 



Arsenic .... 28-36 

 Copper 71-64 



100-00 



B B fuses easily, Avith the odour of arsenic. 



Not soluble in muriatic acid. 



Localities. The Calabazo Mine near Co- 

 quinibo ; Antonio Mine, Copiapo, Chili. 



Name. After M. Domeyko, Professor of 

 Chemistry at Coquimbo. 



DoNACARGYRiTE. A scarcc mineral con- 

 sisting probably of a mixture of several 

 sulph-antimonides of silver and lead. 



Brit. Mus., Case 10. 



DoppLESPA-rti. See Calcite. 



DoPPLERlTE, Dufrenny. An organic 

 compound, occurring in thin plates or mas- 

 si \^e, in peat, near Aussee, in Styria. It has 

 a brownish-biack colour, with a dull brown 

 streak and greasy subvitreous lustre, when 

 fresh ; and a reddish-brown colour by 

 transmitted light when in thin plates. 



Comp. C^ H^ 0^, or, according to Schrot- 

 ter, it is a homogeneous peaty substance, 

 from whose cellulose two parts of water have 

 been removed. 



Annli/$is by Schrotter j 



Carbon 51-63 



Hydrogen . . . .5-34 

 Oxygen . „ . . 43 03 



100-00 

 Name. After Mr. Doppler. 

 DoRANlTE, Thomson^ Greg ^ Lettsom. A 

 zeolitic mineral, probably allied to Anal- 

 cime, in Avhich the soda is replaced by mag- 

 nesia. Occurs in aggregated translucent crys- 

 tals of a yellowish- white colour. S.G, 2-15. 

 Analysis by Thomson : 



Silica ..... 48-00 ' 

 Alumina . . . . 22 00 

 Protoxide of iron . . . 2-75 

 Lime ..... 6-00 

 Magnesia . . . . 13 00 

 Water 7-70 



99-45 



Locality. Two miles W. of Carrick- 

 fergus, CO. Antrim, Ireland ; in basalt. 



Name. After Pat. Doran, late fossil col- 

 lector to the Geological Survey of Ireland. 



Double Fluate of Cerium and 

 Yttkia, Phillips. Double refracting 

 Spar. See Calcite. 



Double refracting Spar. Gelf, Kir- 

 wan. The name given in Hungary to "a par- 

 ticular sort of Argentiferous Copper Pyrites." 



Dragees de Tivoli. Pisolite, which, 

 when broken, exhibits calcareous matter 

 covering a nucleus composed of some other 



DUFRENITE. 



substance, and thus acquiring the appearance 

 of confectionary comfits. 



Dreelite, Dufrenoy. Hexagonal : occurs 

 in small truncated rhombohedrons. Colour 

 and streak white. Lustre pearly ; externally 

 dull, splendent on surfaces of fracture. H. 

 3-5. S.G. 3 3. 



Comp. Sulphate of lime and baryta, or 



CaS + 2Ba S. 



Analysis, by Dufrp.noy : 



Sulphate of baryta . . 61-730 



Sulphate of lime . . 14-275 



Carbonate of lime . . 8 050 



Silica 9-710 



Alumina .... 2-405 



Lime 1-520 



Water .... 2-310 



100000 



BB fuses to a white blistered glass, which 

 is coloured blue by nitrate of potash. 



Localities. In small rhombohedral crystals, 

 disseminated over the surface, and in the 

 cavities of a quartzose rock, near Beaujeu, 

 Dep. of the Ehone, in France. Badenweiler, 

 Baden. 



Named after the Marquis de Dree. 



Drop -stones. Stalagmite. See also 

 Dragees de Tivoli. 



Ducktownite. The name proposed by 

 Prof. C. U. Shepard for a substance Avhich 

 is stated by Prof. G. J. Brush, by whom it 

 has been examined, to be "a mixture of 

 Iron Pyrites, and a rich sulphide of copper, 

 which, if obtained pure, would probably 

 prove to be Copper Glance." It is found at 

 the Ducktown Copper mine, in Eastern Ten- 

 nessee, U.S. 



Dufrenite, Brongniai't. Rhombic : dull 

 leek-green, or blackish-green, in needles, ar- 

 ranged in small radiated masses, with a 

 weak silky lustre. The colour changes on 

 exposure to yellow and brown. Streak olive- 

 green. Slightly translucent. H. 3-5 to 4. 

 S.G. 3-2 to 3-4. 



Comp. Phosphate of peroxide of iron, or 



I^e2p+3H = peroxide of iron 61-32, phos- 

 phoric acid 28'07, water 100-00. 



Analysis, from Haute Vienne, by Vavf 

 quelin : 



Peroxide of iron . . . 56-20 

 Protoxide of manganese . 6-76 

 Phosphoric acid . . . 27-84 

 Water 9-20 



100-00 

 Extremely fusible, melting even in the 

 flame of a candle. 



