ALLOPHANE OPAL. 



Allophane usually occurs lining small ca- 

 vities, and in veins in marl or chalk ; some- 

 times in little reniform masses with a resi- 

 nous or waxy lustre. 



Alt-ophane Opal. See Schrottekite. 



Alloy of Ikidiuini and Osmium, Wol- 

 laston, Phillips. See Iridosmine. 



Alluaudite, Damour, NicoL Occurs 

 massive, Avith a triple cleavage at right an- 

 gles to each other. Colour clove-brown. 

 Subtranslucent or opaqae. Lustre dull. 

 Streak velloAvish. Fracture scaly, shining. 

 H. above 4. S.G. 3-468. 



Comp. (Mn Na)P + #eP+H. 

 ;, Analysis (mean of several) by Damour : 

 Phosphoric acid . . 41-25 



Peroxide of iron . . 25 62 



Protoxide of manganese ., 23-08 

 Peroxide of manganese . 1-06 



Soda 5-47 



Silica 0-60 



Water .... 2-65 



99-73 

 BB on platina wire fuses to a black mag- 

 netic globule. Forms a solution in muria- 

 tic acid Avhich is black when cold, and yel- 

 lowish-brown when heated. 



Locality. Chanteloupe, near Limoges in 

 France, associated with Yivianite and Du- 

 frenite. 



Name. After Mons. Alluaud of Limoges. 



Almagrerite, Breithuupt. An anliy- 

 drous sulphate of zinc occurring in crystals 

 isomorphous with Anglesite and Heavy 

 Spar, at the Barranca Jaroso Mine, in the 

 Sierra Almagrera, Spain. S.G. 4-33. 



Almandine, or Almandine Garnet, is 

 the name given to red transparent varieties 

 of Garnet. It is an alumina-iron Garnet, the 

 composition of which is represented by the 



formula Fe^ Si+Al Si = silica 36-3, alumina 

 20*5, protoxide of iron 43-2 = 100. C'abical : 

 occurs in rhombic dodecahedrons,iand, in the 

 same with all the edges replaced by six- 

 sided planes. Lustre vitreous, shining. Streak 

 white. Fracture subconchoidal, uneven. H. 

 6-5 to 7-5. S.G. 3-7 to 4-21. 



Analysis by Hisinger, from Fahlun : 



Silica 39-66 



Alumina .... 19'66 



Protoxide of iron . . . 39-68 



Protoxide of manganese . 1'80 



1UU-8U 



BB fuses rather readily to a black magnetic 



globule ; with borax more slowly to a dark 



glass, atfording an iron reaction. Insoluble 



in acid. 



ALTAITE. 9 



Localities. This stone is found in sand, 

 alluvial soil, and gneiss, in Ceylon, Pegu, 

 Hindostan, Brazil, (jreenland; also at Elie 

 in Fifeshire, at Ala in Piedmont, and in 

 various parts of Bohemia. 



When of good size, finely coloured, trans- 

 parent, and free from tiaws it is used as a 

 gem. It should be cut quite thin on account 

 of its depth of colour, with a pavilion on the 

 under side and a broad table above, bordered 

 with small facets. An octagonal Garnet, mea- 

 suring 8^ lines by 6^, has sold for near 700 dol- 

 lars. Almandine may be distinguished from 

 Corundum or Spinel by its duller colour. 



Brit. Mus., Case 36. 



31. P. G. Horse-shoe Case, Nos, 889 to 

 893, 897, 898. 



Almandine Ruby. The name given to 

 violet-coloured varieties of Spinel. 



Almandine Spar, Mohs. See Eudia- 



LITE. 



Alstonite, Breithaupt, Nicol, Greg Sf 

 Lettsnm. Rhombic. Primary form a right 

 rhombic prism. Colour snow-white or grey- 

 ish-yellow. Translucent. Lustre vitreous, on 

 surfaces of fracture resinous. Fracture con- 

 choidal, uneven. H. 4 to 4-5. S.G. 3-65 to 3-7. 



Fig. 7. 



Comp. Identical with Barytocalcite. Ba 



C + Ca C, or carbonate of baryta 66*1, carbo- 

 nate of lime 33-9=100. 



Analysis by Thomson, from Fallowfield : 

 Carbonate of baryta . . 60-63 

 Carbonate of lime . . 30-09 



Carbonate of manganese . 9-18 



99-90 

 BB decrepitates and phosphoresces. Dis- 

 solves in acids with effervescence. 



Localities. Fallowfield, near Hexham, 

 Northumberland ; in small six-sided pyra- 

 midal crystals, of a pinkish tinge. Bromley 

 Hill, near Alston (whence the name Alsto- 

 nite) Cumberland ; of a white or grey colour, 

 in veins with Galena. 



Altaite, Dana, Haidinger, NicoL Cu- 

 bical. Usually occurs massive in granu- 

 lar aggregates ; rarely in cubes. Colour 

 tin-white, with a yellow tarnish. Lustre 

 metallic. Sectile. Fracture uneven. H. 3 

 to 3-5. S.G. 810. 



