AKAGONITE. 



BB on charcoal fuses with intumescence, 

 yielding an arsenical odour, and a globule 

 of lead. 



Locality. Dahn, in Bavaria. 



Dr. Krantz suggests that Araaoxene and 

 Dechenite are identical. 



Aragonite, Dana, Brooke &^ Miller; Aka- 

 GONSPATH. Rhombic. Primary form a 

 right rhombic prism. Occurs in hexa- 

 gonal prisms, very frequently in twin 

 crystals, also in globular, reniform, dendri- 

 tic, and corailoid shapes ; sometimes fibrous 

 and in compact masses. (See Flos Ferei 

 and Satin Spar). Colour generally white, 

 but sometimes tinged yellow, blue, and 

 green. Lustre vitreous, inclining to resin- 

 ous on fractured surfaces. Translucent, the 

 small crystals sometimes colourless and 

 transparent, and refracting doubly in cer- 

 tain directions. Brittle. Fracture subcon- 

 choidal. Yields to the knife, but scratches 

 Calc-spar easily. ' H. S'o to 4. S.G. 2'93 to 

 2-94. 



Fig. 30. 



-xPl 



1^ 



Comp. Ca C like Calcite = carbonic acid 

 44-00, lime 56-0=^100. 



Analysis, by Stromeyer, from Aragon : 

 Carbonate of lime . . . 94-82 

 Carbonate of strontia . . 4-08 

 Water 0-98 



99-88 



Thin fragments of transparent crystals 

 decrepitate in the flame of a candle ; other 

 varieties lose their translucency and fall to 

 powder. Becomes phosphorescent on red- 

 hot iron. 



Dissolves with effervescence in nitric 

 and muriatic acids, and paper dipped into 

 a mixture of the solution and alcohol 

 burns with a purple flame. 



Name. This mineral is named after Ara- 

 gon, the province in Spain Avhere it was first 

 discovered in large detached twin hexa- 

 gonal crystals, imbedded with Gypsum in 

 fei-ruginous clay. 



Localities. — English. Various parts of the 

 United Kingdom; in Devonshire, at Tor- 

 bay, in aggregations of acicular crystals 

 with a fibrous structure, and at Ilfracombe, 

 in a spicular form. In fine radiating crys- 

 tals, of a reddish-bi-own colour, at Cleator 

 Moor, in Cumberland — Scotch. At Lead- 



ARFVEDSONITE. 25 



hills, in long, radiating, transparent crys- 

 tals, terminated as in Jig. 30. — Foreign. The 

 most transparent and perfectly defined 

 prisms have been found in a vein travers- 

 ing basalt, at Bilin, in Bohemia. Radiated 

 and minute Avhite crystals occur in the re- 

 cent lavas of Vesuvius. In radiated co- 

 lumnar forms, of a fine green colour, near 

 Gerfalco, in Tuscany. 



Aragonite differs from Calcite in its greater 

 hardness and specific gravity, and in con- 

 taining generally from ^ to 4 per cent, of 

 cai-bonate of strontia, and more rarely from 

 2 to 4 per cent, of carbonate of lead. It may 

 be readily distinguished from Calcite b}' at 

 once flying to powder when exposed to 

 heat, while Calc-spar placed by its side re- 

 mainti unchanged, and does not lose even 

 its transparency. The cleavage planes of 

 Calc-spar are, moreover, always inclined, 

 while those of Aragonite are in a longitudi- 

 nal direction. The calcareous concretions 

 formed in the boilers of steam-engines are, 

 in cases Avhere the incrustations are com- 

 posed of carbonate of lime, almost always 

 Aragonite. 



Brit. Mus., Case 41. 



M. P. G. Slabs A 14—21, in Hall, from 

 Beni- Souef in Egypt. 



Arcanite, Haidinger. See Glasekite, 



Arctizite, Jameson; Wernerite. See 

 Scapolite, 



Arenoalite. a variety of lime-and-iron- 

 Epidote from Arendal, in Norway. The fine 

 crystals from this locality often consist of 

 concentric coats, the exterior of Avhich can 

 be removed, by which means, out of a large 

 and imperfect crystal, one smaller but of 

 a more perfect form can be obtained. S.G. 

 3-4. 



Analysis by Geffken : 



Silica 3G-14 



Alumina .... 22-24 

 Peroxide of iron . . . 14-29 



Lime 22-86 



Magnesia .... 2-38 

 Protoxide of manganese . 2-12 



100-03 



Brit. Mus., Case 35. 



Arfvedsonite, Dana, JVicol; Arfwed- 

 SOMITE, Brooke, Phillips, Allan. A variety 

 of Hornblende containing a large proportion 

 of iron, and also soda. Colour black and 

 opaque. Lustre vitreous, inclining to resin- 

 ous. Streak greyish-green. H. 6. S.G. 3*4 

 to 3-5. 



Comp. ISTa^ Si + Fe Si = silica 49-4, soda 

 11-3, protoxide of iron 39-3 = 100. 



