32 AVENTURINE FELSPAR. 



31. P. G. Horse-shoe Case, Nos. 535 

 to 542. 



AVENTURINE FeLSPAR. See SUNSTONE. 

 AVENTURINE QuARTZ. See AVENTURINE, 



AUGITE, Dana, Nicol, Phillips, Werner. 

 Oblique: a sub-species of Pyroxene, con- 

 fined to the opaque and black or greenish- 

 black varieties common in basaltic and 

 volcanic rocks. It occurs crystallized, but 

 mostly in indeterminately angular pieces 

 and roundish grains. The crystals are 

 generally small and imbedded, and have a 

 vitreous lustre inclining to resinous. Streak 

 varying from white to grey. Fracture un- 

 even, conchoidal. Brittle. H. 5 to 6. S.G. 

 3-33 to 3"36, 



Fig. 32. 



Comp. (Ca, Fe, Mg)^ (Si, Ai)2. 

 Analysis by Von Waltershausen, from Et- 

 na (black) : 



Silica 47-63 



Alumina .... 6-74 

 Magnesia .... 12-90 



LinTe 20-87 



Protoxide of iron . . 11'39 

 Protoxide of manganese . 0-21 

 Water 0'28 



100-02 

 BB fuses, emits a few bubbles, and finally 

 yields a glassy globule, more or less tinged 

 by iron : readily soluble with borax. 



"Localities. — Scotch. Arthur's Seat, Edin- 

 burgh in basalt ; Inchkeith, and in the Isle 

 of Skye.— /ris/t. Portrush, in Antrim, in 

 largc'perfect, black crystals; also at Fair- 

 head in larger but less perfect crystals.— 

 Foreign. In very fine crystals imbedded 

 in basalt, at Aussig and Toplitz in Bohemia, 

 and in some of the scorias of Monti Rossi, 

 on Etna; also in the volcanic regions of 

 Vesuvius (in small brilliant crystals), Strom- 

 boli, Auvergne, the Eifel, Teneriffe, Bour- 

 bon, and numerous other localities. 



Name. From <x-vy'i, brilliancy. 



Augite forms an important constituent 

 in basaltic and volcanic rocks, but it is 

 never found in granite rocks. The crystals 

 met with in basalt are generally larger 

 than those found in lava. 



Brit. Mus., Case 34. 



M. P. G. Horse-shoe Case, Nos. 1034 to 



AURIFEROUS PYRITES, 



1038, 1042: Upper Gallery; Wall • case 1, 

 Nos. 37 to 41 : Table-cases A. and B. 

 AuiNA, 3Ionticelli. See Haxjyne. 

 AuERBACHiTE. A mineral nearly allied 

 to Zircon in form and composition, but 

 differing from it in inferior hardness and 

 specific gravity, and greater fusibility with 

 potash. Probably it is altered Zircon, in 

 which a portion of the zirconia is removed. 

 Pyramidal. Colour brownish-grey. Lustre 

 weak, greasy. H. 6'5. S.G. 4-06. 



BB alone infusible : fuses with hydrated 

 potash. 

 Comp : 



Silica 42-91 



Zirconia .... 65-18 

 Oxide of iron . . . 0-93 

 Unknown and loss . . 0-95 



99-97 

 It was named by Hermann after Dr. 

 Auerbach. 



AuRiCHALCiTE, Bottger, Dana. A car- 

 bonate of zinc and copper, occurring in 

 acicular crystals, forming drusy incrusta- 

 tions, or in fibrous, silky, and divergent 

 groups; also, laminated, or columnar and 

 granular. It is translucent, with a pearly 

 lustre, and varies in colour from pale green 

 to verdigris-green. H.2. 



Comp. 2(Zn, Cu) C + 3(Zn, Cu,) H, or 

 oxide of copper 29 2, oxide of zinc 44-7, 

 carbonic acid 19-2, water 9-9 = 100. 

 Analysis by Bottger, from the Altai : 

 Oxide of zinc . . . 45-62 

 Oxide of copper . . 28-35 

 Carbonic acid . . . 16-07 

 Water . . . .9 93 



99-97 

 BB gives out water in a matrass, and green 

 crvstals become brownish-black. In tht 

 outer flame does not fuse, but in the inner 

 flame forms a slag, which is yellow while 

 hot, but white on cooling. Yields a greeu 

 glass with borax and salt of phosphorus. 

 Soluble with effervescence in muriatic acid. 



Localities. — English : in small groups of a 

 pale-green colour and laminated structure, 

 at the Rutland mine, near Matlock, in 

 Derbvshire, and at Roughten Gill, in Cum- 

 berland. — Foreign. Loktefskoi, a copper- 

 mine in the Altai, forming a drusy covering 

 on Calc-spar and Brown Iron-ore ; and at 

 Reszbanva, in Hungary. The Green Cala- 

 mine of Patrni is a variety of Aurichalcite, 

 found in cavities, near Cleopinski. 



Auriferous Pyrites. Iron Pyrites con- 



