JEWREINOWITE. 



words, Jayet, Jais, or Jet are doubtless de- 

 rived from the ancient name Gagates or 

 Gagat. 



Artificial Jet is made of a kind of black 

 glass, wliicb is either cut into facets or 

 blown into beads ; and the blackness is pro- 

 duced by means of the black wax with 

 which they are filled, or which fastens them 

 to the iron backs on which they are mounted. 



*' Lycia her jet* in medicine commends ; 

 But chiefest, that which distant Britain sends : 

 Black, light, and polished, to itself it draws 

 If warmed by friction near adjacent straws. 

 Though quenched by oil, its smouldering embers 



raise 

 Sprinkled with water, a still fiercer blaze : 

 It cures the dropsy, shjtkey teeth are fixed. 

 Washed with the powder'd stone in water 



mixed. 

 The female womb its piercing fumes relieve, 

 Nor epilepsy can this test deceive ; 

 From, its deep hole it lures the viper fell, 

 And chases tar away the powers of hell ; 

 It heals the swelling plagues that gnaw the 



heart. 

 And baffles spells and magic's noxious art. 

 This by the wise the surest test is styled 

 Of virgin purity by lust defiled. 

 Three days in water steeped, the draught 



bestows 

 Ease to the pregnant womb in travail's throes." 



Brit. Mus., Case 60. 



M.F. G. Horse- shoe Case, Nos. 89 and 90. 



Jewkeinowite. See Jefkeinoffite. 



Jews' Pitch. See Asphalt. 



Jews' Tin. The name given in Cornwall 

 to tin found near old smelting houses. 



Johannite, Haidinger. An ore of Ura- 

 nium. Oblique ; primary form an ob- 

 lique rhombic prism. Occurs in very 

 minute flattened crystals, Jig. 247, arranged 

 in concentric druses or reniforni masses. 

 Colour beautiful, deep grass-green. Lustre 

 vitreous. Transparent to opaque. Taste 

 slightly bitter. Streak pale siskin-green. 

 Fracture imperfect-conchoidal. H. 2 to 2-5. 

 S. G. 3-19. 



Fig. 247. \^ 



Comp. 2(U ^) S + Cu S + 4H = sul- 

 phuric acid 19-37, oxides of uranium 68-40, 

 oxide of copper 6-43, water 5-80 = 100. 

 Analysis (mean of two), by Lindaker : 

 Sulphuric acid . . . 20-02 

 Oxide of uranium . . 67-72 



* Lapidarium (xviii.) of Marbodus, from 

 " Antique Gems, their Origin, Uses and Value," 

 Ijj Rev. C. W. King, M.A. 



JUNCKERITE. 



Oxide of copper . 

 Protoxide of iron . 

 Water .... 



19; 



5-99 

 0-20 

 5-59 



99-52 



In a glass tube gives off water and sul- 

 phurous acid when highly heated, and be- 

 comes brown and finally black. BB on 

 charcoal gives sulphur-fumes and a scoria of 

 a black colour and dull green streak. 



Locality. Near Joachimsthal, in Bohemia. 

 Johanngeorgenstadt, in Saxony. The Mid- 

 dletown felspar quarry, in the United States. 



Name. After the late Archduke Johann 

 of Austria, a zealous mineralogist. 



Brit. Mus., Case 55. 



Johnite. a variety of Turquois, occur- 

 ring in mammillary, stalactitic, and bo- 

 tryoidal masses, disseminated in siliceous 

 schist. Colour bluish -green. H. 3. 



Comp. Like Turquois, or a sub-phosphate 

 of alumina, coloured by copper and iron. 



Analysis, by John ; 



Alumina .... 44*50 

 Phosphoric acid . . . 30-90 

 Oxide of copper . . . 3-75 

 Protoxide of iron . . .1-80 

 Water 19-00 



99-05 



Locality. Jordansmiihle, in Silesia. 



Johnstonite, Haidinger. A finely granu- 

 lar Galena, mixed with more or less free sul- 

 phur. Massive. Opaque. Colour bluish. 

 Lustre metallic. H. 3. S.G. 6-7. 



Comp. Supersulphide of lead, or galena 

 90-38, sulphur 8-71 = 100. (Johnston!) 



Localities. Dufton, in Westmoreland. 

 Alston, in Cumberland. Cromford, in Der- 

 byshire. Glen Malure, in Wicklow. — 

 Foreign. The lead mines Neu-Sinka, near 

 Fogaras, in Transylvania. (See Sinka- 

 nite.) In a vein in the Siegen mining dis- 

 trict in the Rhine provinces, where it is 

 known among the miners by the name of 

 " burning galena," and is associated with un- 

 altered Galena, some sulphate of lead, and 

 a small quantity of sulphur. 



Name. After Johnston, by whom it was 

 first described. 



Brit. Mus., Case 38. 



Judenpech, Wiedenman. See Asphalt. 



JuNmcERiTE, Dufrtiioy. Occurs in yel- 

 lowish-grey rhombic pyramids, with cleav- 

 age perpendicular to the axis, and parallel 

 to two diagonals. It therefore exhibits, 

 with regard to Spathic Iron, the same 

 dimorphism that Aragonite exibits with 

 regard to Calc Spar. Breithauptj on the con- 

 o3 



