ALEXANDRITE. 



Epidote and Garnet ; Greenland,with Eudy- 

 alite and Hornblende; Massachusetts, tl. 

 S., with Tourmaline; Siberia; Norway; 

 iSweden ; Bohemia ; Oisans, in Dauphiny ; 

 and elsewhere. 



Name. From albus (white), in allusion to 

 its colour. 

 Brit. Mus., Case 30. 

 M. P. G. Horse-shoe Case, No. 953. 

 Albite is a soda Felspar, a small portion of 

 the soda being sometimes replaced by pot- 

 ash and lime. It is frequently a constituent 

 of granite, and, more frequentjjy than com- 

 mon Felspar, of syenite and greenstone (as 

 in the rocks round Edinburgh) ; but it often 

 occurs associated with the latter in the same 

 granite, when it may be distinguished by 

 its greater whiteness and translucency. 

 Thus, in the granite of Pompey's Pillar, 

 and the block on which the statue of Peter 

 the Great in St. Petersburg is placed, the 

 Albite presents a greenish-white colour, 

 while the Felspar is flesh-red. 



Alexandrite. A variety of Chryso- 

 beryl found in mica-slate Avith Beryl and 

 Phenacite, 85 wersts from Ekatherinenberg 

 in the Ural. It is of an emerald-green 

 colour by reflected light and columbine-red 

 by transmitted light. The colour is sup- 

 posed to be produced by the presence of 

 oxide of chrome. Named after Alexander 

 I., Emperor of Russia. 

 Brit. Mus., Case 19. . 

 Algerite. An altered form of Scapolite. 

 Occurs in slender square prisms imbedded 

 in Calc-spar. Colour yellowish to grey. 

 Usually dull. Brittle. H. 3 to 3-5 : of more 

 altered crystals 2-5. S.G. 2*7 to 2'78. 

 Analysis bv T. S. Hunt : 



Silica \ . , . 49-82 

 Alumina , . . 24'91 



Magnesia . . . 1-15 



Potash .... 10'2l 

 Carbonate of lime . . 3.94 



Water .... 7-57 



97-60 



Locality. Franklin, Sussex co., New Jer- 

 sey. 



Name. After Alger, the American minera- 

 logist. 



Algodonite. a new mineral found in 

 small white lumps and veins, (at first sup- 

 posed to be native silver,) in the silver- 

 mine of Alogodes (whence the name Algodo- 

 nite) near Coquimbo in Chili. 



Comp. A compound of arsenic and copper 

 in which the proportion of copper is twice 

 that in Domevkite, or Cui2 AS, or copper 

 83-66, arsenic 16 -34 = 100. 



ALLANITE. 7 



Analysis by F. Field : 

 Copper .... 83-30 



Arsenic .... 16-23 



Silver ..... 0.31 



99-84 

 Colour brilliant silver-white ; also white, 

 but quickly tarnishes on exposure to the air. 

 Fracture strong gr-anular. Soluble in di- 

 lute nitric acid. 



Alisonite, F. Field. Massive. Colour 

 deep indigo-blue, quickly tarnishing on ex- 

 posure. Fracture slightly conchoidal. H. 

 2-5 to 3. S.G. 6-1. 



Comp. Double sulphide of copper and lead 

 or 3Cu2S + Pb S = copper 53-33, lead 28-80, 

 sulphur 17-77 = 100. 



Analysis by Frederick Field : 

 Copper .... 63-63 

 Lead .... 28-25 

 Sulphur .... 17-00 



98-88 



Violently acted on by nitric acid with the 

 formation of sulphate of lead and liberation 

 of free sulphur. 



Locality. Mina Grande, near Coquimbo, 

 Chili, associated with carbonate of lead and 

 carbonate of copper. 



Name. After R. E. Alison. 



Alizite, Glocker, See Pimelite. 



Alkali minerale, Broehant. See Na- 

 tron. 



Allagite. a compact variety of Rhodo- 

 nite, altered through the tendency of prot- 

 oxide of manganese to pass to a higher state 

 of oxidation, accompanied Avith the absorp- 

 tion of water. It is of a greenish-grey 

 colour, verging upon black, and is some- 

 what fibrous, resembling altered Busta- 

 mite. 



Analysis by Du Menil : 

 Peroxide of manganese . 75-0 

 Silica .... 16-0 

 Lime .... 7-5 



98-5 



Locality. The vicinity of Rubeland in the 

 Harz. 



Name. From «AX«y'<, change ; in allusion 

 to its change on exposure. 



Brit. Mus., Case 26. 



Allanite. PhilUps, Thomson, Nicoh 

 Dana. Oblique. Isomorphous with Epi- 

 dote. Occurs in long and slender, or flat 

 tabular crystals, or in masses and grains. 

 Colour black, passing into reddish- or green- 

 ish-brown Opaque ; feebly translucent and 

 of a yellowish- brown colour in thin splin- 

 ters. " Lustre submetallic, inclining to vi- 

 treous or resinous. Streak greenish-grey. 

 b4 



