196 JEFREIXOWITE. 



line masses, of a dark olive-green colour, 

 passing into brown, with a semimetallic 

 lustre on the planes of cleavage, on the cross 

 fracture resinous. Translucent at the edges. 

 Yields to mechanical division in three di- 

 rections. H. about 4-5. S.G, 3-6. 



Comp. _ (Ca, Fe, Mg, Zn)5 Jsi^ 



. 



Analysis, by Hermann : 





Silica .... 



49-91 



Alumina 



1-93 



Lime .... 



15-48 



Protoxide of manganese 



7-00 



Oxide of zinc 



4-39 



Protoxide of iron 



10-53 



Magnesia 



8-18 



Loss by ignition . 



1-20 



98-62 



BB fuses readily to a black globule. Par- 

 tially soluble in heated muriatic acid. 



Locality. IMine Hill, and Franklin iron- 

 works, near Sparta, in Sussex County, New 

 Jersey, associated with Franklinite and 

 Garnet. 



Name. In honour of Jefferson, President 

 of the United States. 



Brit. Mus., Case 34. 



Jefreixowite. a variety of Idocrase, 

 sometimes colourless, but generally of a yel- 

 lowish-brown colour. 



Analysis, by Ivanow : 





Silica . . . 



. 37-41 



Alumina 



. 20-00 



Peroxide of iron . 



. 4-60 



Lime . 



. 34-20 



Potash . 



. 1-16 



Soda . 



. 1-70 



99-07 



Locality. Finland. 



Jellelite. The mineral to which this 

 name was given by Apjohn is merely a 

 Garnet. It occurs in Ireland, in rhombic 

 prisms, as a yellowish, slightly greenish, 

 incrustation, and is compact in texture. 



It is composed of silica 38'09, peroxide of 

 iron 33-41, lime 28-61 = 100. (Wright.) 



Jenite. a name for Lievrite, bestowed 

 by the French in commemoration of the 

 battle of Jena. 



Jenkinsite, Shepard. A variety of Hy- 

 drophite, occurring as a fibrous incrustation 

 on Magnetite. Colour blackish-green, often 

 with a tinge of olive. In powder pistachio- 

 green Translucent. Lustre vitreous. H. 2-6. 

 S.G. 2-4 to 2-6. 



Analysis, by Smith 8f Brush : 



Silica 38-97 



Alumina . . , » 0-53 



JET. 



Protoxide of iron . 



Protoxide of manganese 



Magnesia 



Water .... 



19-30 



4-36 



22-87 



13-36 



99-39 



Locality. O'^eil's mine, Orange co., U. S- 



Name. After Mr. John Jenkins, of Monroe. 



Jet, Kirwan. A variety of Lignite. Co- 

 lour velvet-black, or brownish-black, when 

 passing into bituminous wood. 



It occurs in elongated reniform masses, 

 and sometimes in the shape of branches, 

 which exhibit a regular woody internal 

 structure, by transmitted light, when cut in 

 extremely thin slices. Lustre brilliant and 

 resinous. Sectile and brittle, breaking with 

 a large and perfect conchoidal fracture ; and 

 often showing a tendency to divide into pris- 

 matic or columnar masses. It feels remark- 

 ably smooth and does not stain the fingers. 

 Slightly heavier than water. Burns with a 

 greenish flame, and emits a very strong, 

 sweetish bituminous smell, leaving a light 

 yellowish-coloured ash. 



Localities. Jet is found principally in 

 marly, schistose, or sandy beds in France ; 

 near Wittemberg in Prussia ; in the amber 

 mines on the coast of the Baltic, where it 

 is known by the name of Black Amber ; 

 and in Alum shale in the neighbourhood of 

 Whitby in Yorkshire, in hard and dark- 

 coloured bituminous shale forming the 

 lower part of the Upper Lias formation. 

 Jet is made into various articles, and is 

 especially used for mourning-ornaments. 

 The value of the jet manufactured at Whit- 

 by in 1855, amounted to £20,000. In 

 France the departments of Aude, of the 

 Var, the Pyrenees, of Ariege, and of Arden- 

 nes are celebrated for this production. In 

 the last century 1200 men were employed 

 in the department of the Aude alone, in 

 carviiag and turning the Jet of that neigh- 

 bourhood into beads, rosaries, buttons, 

 bracelets, earrings, necklaces, snuff-boxes, 

 drinking vessels, and into pieces cut iu 

 facets, for mourning ornaments. 1000 cwts. 

 were yearly consumed for these purposes, 

 but the trade has now greatly fallen off. 

 Considerable quantities are still, however, 

 exported to Turkey, Senegal, but chiefly to 

 Spain, to which latter country Jameson 

 states that manufactured Jet to the value 

 of 18,000 livres was sold in 1805. 



This substance is the Gagates of the an- 

 cients, who gave it that name after tlie 

 River Gaga, or the town of Gagis in Lycia, 

 where it was originally found. The modern 



