116 DIPYRE. 



DiPRiSMATic Olive Malachit, Moh ^ 



See LiBETHENITE, 



DiPYKE, HaiLy. Occurs in slender, indis- 

 tinctly formed, four-sided prisms, rounded 

 at the ends, and resembling grains of wheat ; 

 also in small fascicular masses. Colour grey- 

 ish-white or reddish-white. Lustre vitreous. 

 Translucent to transparent. Opaque in 

 weathered specimens. Easih'- frangible, lon- 

 gitudinal fracture foliated. Scratches glass 

 H. above 4 when fresh. S.G. 2-64. 



Comp. 4 (Ca, Na) Si 



+ 3 



Al,Si = silica 



53-8, alumina 



26-2, lime 



y-5 



, soda 10-5 = 



100-0. 









Analysis by 



Deksse : 







Silica . 







. 55-5 



Alumina 







. 24-8 



Lime 







. 9-0 



Soda . 







. 9-4 



Potash . 







. 0-Y 



99-4 



BB fuses with effervescence to a white 

 blebby glass. 



Attacked with much difficulty by the 

 strongest acids. 



Lucalities. A torrent near Mauleon, in the 

 Western Pyienees, with Talc or Chlorite, 

 in a soft clay-slate; Valley of Castillon, 

 especially at Angomer. 



Name. Yrom ^'s, double, and ^iJ?, Jire ; in 

 allusion to the double effect of fire upon it, 

 by fusing it, and rendering it slightly phos- 

 phorescent. 



Brit. Mus., Case 31. 



DiKHOMBOHEDRAL EuTOME GlANCE, 



Mohs. See Molybdenite. 



DisCRASE, Leymerie ; DisCRASTTE, Frohel. 

 Ehombic: occurs in hexagonal prisms and 

 stellate forms; also massive, disseminated, 

 or in grains. The surfaces of the prisms are 

 usually deeply striated longitudinally ; but 

 those of other forms are smooth. Colour and 

 streak between silver-white and tin-white, 

 generally inclining to the former, often tar- 

 nished yellow or reddish. Lustre metallic. 

 Opaque." Structure lamellar. Easilj' frangi- 

 ble. Fracture flat conchoidal. Soft. Slightly 

 malleable. H. 3-5 to 4-0. S.G. 9-44 to 9-8. 



Comp. Antimonide of silver, or Ag*, Sb 

 =silver 77-01, antimony 22-99 = 100. 



Analysis, of a coarse-grained specimen 

 from Wolfach, by Klaproth : 



Silver . . . . .76 

 Antimony 24 



100 

 BB on charcoal, fuses readily, giving off 

 antimonial fumes, which stain the charcoal, 



DODECAHEDRAL GARNET. 



and is reduced to a grey, brittle, metallic 

 globule, which becomes white on continu- 

 ing the heat, and solidifies, with incan- 

 descence, to a crystalline globule on cooling, 

 which, by further blowing, is converted into 

 pure metallic silver. 



Soluble in nitric acid, leaving oxide of 

 antimony. 



Localities. Altwolfach in Baden, and Wit- 

 tichen in Swabia, in veins, with Galena, 

 Native Silver, Iron Pyrites, Blende, and 

 other ores, in granite. In clay-slate, at 

 Andreasberg, in the Harz, Allemont, in 

 Dauphine. Casalla, near Guadalcanal, in 

 Spain. The Goldberg, in Rauris, Salzburg. 

 Near Coquimbo, S. America, &c. 



If this mineral were less rare, it would be 

 a valuable ore of silver. It may be distin- 

 guished from Native Silver by its brittle- 

 ness and foliated fracture; from Smaltine 

 by its fracture, which is foliated instead of 

 granular and uneven ; from Arsenical Pyrites 

 by fracture and hardness, the Pyrites hav- 

 ing a fine-grained, uneven fracture, and 

 giving sparks with steel. {Jameson.) 



Name. From ^'V, two-fold, and x^a.ins^ mix- 

 ture, in allusion to its composition. 



DisoMosE, Beudant. See Gersdorffite. 

 The name is derived from ^k, twice, and 

 oM,o<o?, like, because the formula is the same 

 as for Grey Cobalt, where cobalt replaces 

 nickel, and as for Antimonickel where anti- 

 mon}^ replaces arsenic. 



DisTERlTE, Dufrenoy; Disterrite. A 

 variety of Clintonite, occurring in hexa- 

 gonal prisms, in the valley of Fassa, Tyrol. 

 H. of base 5; of sides 6 to 6-5. S.G. 3-04 

 to 3-05. 



Analysis by v. Kohell : 



Silica 20-00 



Alumina .... 43-22 

 * Magnesia . . . .25-01 



Lime 4-00 



Potash 0-57 



Peroxide of iron . . .3-60 

 Water ..... 3-60 



100-00 



See Brandisite. 



DisTHENE, Haiiy. (from ^h, double, and 

 (rdivos^ strength.) A name given by Haiiy to 

 Kyanite, on account of its double electric 

 powers; some crystals acquiring negative, 

 others positive electricity by friction. 



Dodecahedral Corundum, Mohs. See 

 Spinel. 



Dodecahedral Dystome Glance, Jib/ts. 

 See Tennantite. 



Dodecahedral Garnet, Mohs. See 

 Garnet. 



