DTALLAGE CHATOYANTE. 

 Harzburg in ihe Harz. Massive or disse- 

 minated near Geneva, and on Monte Rosa in 

 Switzerland. 



Name. From J/aAAayij, difference, alluding 

 to the dissimilar cleavage. 



Brit. Mus., Case 2o, 



M. P. C, Horse-shoe Case, 1088. Upper 

 Gallerj', Wall-case 5, Nos. 10 to 37, 



DiALLAGE Chatoyante. See Schiller- 

 spar. 



DiALLAGE FlBRO LAMINAIRE MeTAL- 



LOiDE, Haiti/. See Bronzite. 



DiALLAGE Metalloidk, Haili/. See 

 DiALLAGE and Hypeksthene. 



DiALLAGE Vekte, Haily. See Smarag- 



DITE. 



DiALLOGiTE, Beudant. Hexagonal : pri- 

 mary form a rhomb. Occurs very com- 

 moDly in saddle-shaped lenticular crystals; 

 also massive. Colour rose red and flesh -red. 

 Lustre vitreous inclining to pearly. Trans- 

 lucent, Streak white. Structure lamellar. 

 Scarcely scratches glass, and yields to the 

 knife. Brittle. Fracture uneven. H. 35 to 

 4-5. S.G. 3-4 to 3-6. 



Fig. 144. 



Comp. Mn C= carbonic acid 38-2, protoxide 

 of manganese, 61-8 = 100-0. The Mn is 

 usually replaced partially by Ca, Fe, and 

 Mg ; so that the composition may be repre- 

 sented generally by tbe formula (Mn, Ca, 



Fe, Mg) C. 



Analysis, from Freiberg, by Stromeyer : 

 Carbonate of manganese . 73 70 

 Carbonate of lime . . 13118 

 Carbonate of iron * . . 5-76 

 Carbonate of magnesia . 7*26 

 Water 0-05 



99-85 



Decrepitates when heated. 



BB becomes brown or greyish-black, but 

 is infusible without addition. 



Very slowly soluble in cold, and rapidly 

 in warm muriatic acid. 



On exposure to the air assumes a brown 

 tint, and the bright rose-red varieties be- 

 come paler. 



Localities. — English. The mines near 

 Oswe.str}', in Shropshire. Hartshill, War- 

 wickshire. — Irish. Glendree, near Tulla, co. 



DIAMOND. ' 109 



Clare, &c. — Foreign. Freyberg and other 

 mines in Saxony. Those of kapnik,Nasyag, 

 andOffenbanya in Transylvania. Near El- 

 bingerode in the Harz. In a pulverulent 

 form, coating Triplite, at Washington, Con- 

 necticut, U.S. Placentia Bay, Newfound- 

 land ; of a fawn or chestnut -brown colour 

 in Silurian slates. 



Diallogite may be distingyiished from 

 Rhodonite, or Manganese Spar, by its in- 

 ferior hardne-s. It generally occurs in me- 

 talliferous veins with ores of silver, lead, and 

 copper, as well as with other ores of manga- 

 nese, both massive and in botryoidal con- 

 cretions lining cavities. 



Brit. Mus., Case 34. 



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

 13 (British). 



DiAMANT. 

 DiAMANT 



Quartz. ' 



Diamond. Cubical. Frequently in twin 

 crystals, with faces often convex. Plane of 

 composition octahedral. Cleavage highlj^ 

 perfect. Rarely massive. Lustre brilliant ada- 

 mantine. Colour white or colourless, occa- 

 sionally with tints of .yellow, red, orange, 

 green, brown, or black. Transparent to 

 translucent when dark coloured. Fracture 

 conchoidal. H. 10. S.G. 3-5295 to 3-55. 



Exhibits vitreous electricity when rubbed. 



Index of refraction 2-439, being often irre- 

 gular, owing probably to the same cause 

 which has produced the convexity of its 

 forms. 



Becomes phosphorescent on exposure to 

 the light, and the smaller Diamonds become 

 phosphorescent by a much shorter exposure 

 than those of larger size. 



French for Diamond. 

 d'Alencon. See Smoky 



Fig. 14G. Fig. 147. 



Comp. Pure carbon crystallized. Burns 



