LABRADOR FELSPAR. 

 Labrador FelsPxIr, Phillips. Labra- 

 DORiTE, La 3Ietherie. Labradorstein, 

 Werner. Labradorestone, Kirwan. A 

 variety of Felspar sometimes used for orna- 

 mental purposes on account of its beautiful 

 chatoyant reflections. Anorthic ; frequently 

 occurs in twin crystals like those of Albite. 

 Colour smoke-grey, dark ash, brown, green- 

 ish, white, red and blue. Lustre vitreous, 

 inclining to pearly on the faces of most 

 perfect cleavage, to sub-resinous on the 

 other surfaces. Streak white. Brittle. 

 Fracture imperfectly conchoidal, uneven, 

 splintery, H. 6. S.G. 2-67 to 2-76. 



Fig. 250. 



Comp. Kbi + Al bi = (ii + Al) Si where 



K=Na and Ca : if Na be to Ca in the pro- 

 portion of 1 to 3, then the formula becomes 



NaSi + oCa Si + 4A1 Si = silica o3-69,alumina 

 20-68, lime 12-13, soda 4-50 = 100. 



Analyses, (a) from Labrador, by Klaproth; 

 (b) from Campsie, by Lehunt : 



(«) W 

 Silica . . . 55-75 64-67 

 Alumina . . 26-50 27-89 



Peroxide of iron . 1*25 0-31 

 Lime . . . 11-00 10-60 

 Soda . . . 4-00 6-05 



Potash . . . 0-00 0-49 

 Magnesia. . . 0-00 0-18 

 Water . . . 0-50 



99-00 99-19 



BB on charcoal, behaves like Felspar, and 

 fuses with rather less difficulty to a colour- 

 less glass. Yields a blue pearl with borax 

 and oxide of nickel. 



When powdered, entirely dissolved by 

 heated muriatic acid, which does not act 

 either on Felspar or Albite. 



Labradorite occurs chiefly as a constituent 

 of rocks ; also in the lavas of Etna and 

 Vesuvius, in the Oriental verde antique of 

 Greece and other porphyries, as well as in 

 certain hornblendic rocks, granites and 

 syenites. 



Localities.— Scotch. It is found in Stir- 

 lingshire in porphyritic greenstone, at Camp- 

 sie, and at Milngavie in small crystals. — 

 Irish. In Ireland it is met with in the 

 basalt of Magee Island, co. Antrim : Mourne 



LAGOXITE. 207 



Mountains, co. Down, and in Galway finely 

 crystallized and exhibiting a display of 

 colours. — Foreign. Finland. Russia. IVrol. 

 The Harz. Corsica. Saxon}'. Sweden. 

 Faroe. Norway. Canada at Granville, Cape 

 Mahue, Abercrombie &c. United States. 

 On the coast of Labrador, whence it was 

 originally brought, it is associated with 

 Hornblende, Hypersthene, and Magnetic 

 Iron -ore. 



Labradorite takes a fine polish, and on 

 account of its beautiful chatoyant reflections 

 it is valued for ornamental purposes, and 

 sometimes used in jewelry. "Besides the 

 fundamental colour, it presents a most beau- 

 tiful play of vivid tints, varying according 

 to the position in which it is viewed. Of 

 blue, it exhibits all the varieties from violet 

 to smalt-blue ; of green, it displays the pure 

 emerald -green, and various other tints ap- 

 proaching to blue on the one hand, and to 

 yellow on the other. Of yellow, the most 

 usual shades are golden and lemon-yellow, 

 verging into deep orange, and thence into 

 rich copper-red and tombac-brown. The 

 parts exhibiting these beautiful colours are 

 disposed in irregular spots and patches, and 

 the same spot, if held in diff"erent positions, 

 displays various tints : of these violet and 

 red are the most rare." (Ilawe.^ The play 

 of colour is supposed by some to be pro- 

 duced by microscopic crystals of Quartz 

 imbedded in the stone ; by others it is re- 

 ferred to the structure of the Felspar itself. 



It is manufactured into brooches, pins, 

 bracelets &c., also into snuff"-boxes and 

 similar articles. It looks best when cut in 

 plain, very flat cabochon ; a great deal of 

 skill is required to divide the stone in such 

 a manner, that the iridescent portions, on 

 which its beauty depends, may be displayed 

 to the utmost advantage. 



Brit. Mus., Case 30. 



3L P. G. Horse-shoe Case, Nos. 961 

 to 964 ; also on Floor at S.W. end of Case. 



Labrador Hornblende. See Hyper- 

 sthene. 



Lagonite. An earthy mineral of an 

 ochreous-yellow colour, occurring as an in- 

 crustation at the lagoons of Tuscany. 



Comp. Fe B^ + 3H=boracic acid 49-5, 

 peroxide of iron 37-8, water 12-7 = 100. 



Analysis, by Bechi : 



Boracic acid .... 47-95 

 Protoxide of iron . . . 36-26 

 Magnesia, lime, and loss . 1-77 

 Water 14-02 



100-00 



