JAROSITE. 



and yellow of various shades, but generally 

 smoky and ill- defined. It occurs in worn 

 angular pieces, or in small detached crystals, 

 rarely exceeding 6 or 8 carats in weight, 

 chiefly in the sand of a river in Ceylon, ac- 

 companied by Sapphire, Spinelle, Tourma- 

 line, &c. 



The surfaces of the crystals are smooth, 

 and possess a lustre approaching nearer to 

 that of the Diamond than any other gem. 



About the commencement of the last cen- 

 tury, when the Jargoon was supposed to be 

 an inferior variety of Diamond, it was in 

 great request, espe'cially for mourning orna- 

 ments, for Avhich it was considered to be 

 peculiarly appropriate, on account of its 

 sombre tone, and almost adamantine lustre. 



At the present day, though out of fashion, 

 and in no request, it is still occasionally 

 sold for inferior diamonds. 



Dr. J. Davy says, that the very light grey 

 varieties of the Zircon are sold by the in- 

 habitants of Cejdon as imperfect diamonds, 

 the natives being altogether ignorant of the 

 true nature of the mineral. It is most 

 abundant in the district of Matura, whence 

 it has its common name in Ceylon of 3Ia- 

 tura diamond. The colourless Zircon is also 

 cut and sold as a false diamoiid in the 

 bazaars of India. (Prinsep.) 



M. P. G. Horse-shoe Case, No. 846. 



Jarosite, Breithaupt. A potash copperas. 

 Hexagonal. Cleavage basal. Colour yel- 

 lowish. 



Comp. KS + 4Feb + 6H( + i^"eH). Eam- 

 nielsberg. 



Analysis, bv Richter ; 



Sulphuric acid . . . 28-8 

 Peroxide of iron . . . 52'5 

 Alumina . . . .1*7 

 Potash with a little soda . 6-7 

 Water 9-2 



98-9 



Locality. Earanco Jaroso, in the Sierra 

 Almagrera, in Spain. 



Jasp-Opal. See Opal- jasper. 



Jaspachates. The name by which Jas- 

 per-agate was known to the ancients. 



Jaspe Rubane, Brochant. See Ribbon 

 Jasper. 



Jasper. A compact variety of Qiiartz, 

 usually of a dull red, yellow, brown, or 

 green colour, sometimes blue or black, and 

 distinguished from other varieties of Quartz 

 by its complete opacity, even in very thin 

 slices. 



Jasper is fre'quently merely a form of silex 

 rendered opaque either from alteration or 



JEFFERSONITE. 195 



b}' the addition of a certain quantity of red 

 oxide of iron, or the hydrate of that oxide. 



When the colours are arranged in stripes, 

 it is called striped or ribbon- jasper. 



Egyptian Jasper occurs in the form of peb- 

 bles on the banks of the Nile, and is zoned 

 with red and various shades of wood -brown 

 fancifully intermixed with, and contrasted 

 by, paler cream-coloured portions. 



Porcelain Jasper is altered (or baked) 

 clay, differing from true Jasper in being 

 fusible at the edges BB. 



Yellow Jasper is found at Yourla, in the 

 Bay of Smyrna, and pebbles of i?t'«i Jasper 

 on\he plains of Argos. 



Jasper is susceptible of a brilliant polish, 

 and is manufactured into brooches, brace- 

 lets, snuft-boxes, vases, knife-handles, and 

 other ornamental articles. 



It occupied the twelfth place amongst the 

 precious stones which were ordered to be 

 placed on the breast-plate of the High 

 Priest of the Jews, and bore the name of 

 Benjamin engraved upon it. (Exodus 

 xxviii. 20.) See also Ezekiel xxviii. 13 ; 

 Rev. iv. 3; xxi. 11, 20. 



Name. The word Jasper is derived from 

 "laa-^i;^ the name given by the ancients not 

 only to the Jasper of the moderns, but to 

 some other stones not of the true Jasper 

 kind. 



" Bright are the jasper's* tints, with clouds, 

 And spots, and diverse stripes, and splendid 



veins 

 Of green and various hues ; in mass opaque, 

 But in thin fragments pervious to the light : 

 With earthy fracture angularly sharp, 

 Less hard than flint, but striking fire with steel. 

 Jasper in large elliptic masses oft 

 Occurs, or nodes detached, or rocks entire, 

 To which Egyptian pebble's near allied." 



Brit. Mus., Case 24. 



M. P. G. Horse-shoe Case, ISTos. 563 to 

 568. 



Jaspery Iron Ore, or Jaspery Clay- 

 iron. An earthy variety of Hematite, hav- 

 ing a fu-mer structure than Reddle or Red 

 Chalk, and a large and flat conchoidal frac- 

 ture. 



Jadlingite. a mineral resin, found be- 

 tween the layers of a kind of pine-tree at 

 the lignite mine of Jauling, near Saint Veit 

 in Austria. 



Jay. a name given by the colliers in 

 Derbyshire to Can n el Coal. See Jet. 



Jayet, Haiiy. See Jet. 



Jeat, Woodward. See Jet. 



Jeffersonite, Phillips. A variety of 

 Pyroxene, occurring in foliated or crystal - 



* Werneria, or Short Characters of Earths, by 

 Terrse Filius, 1805. Pp. 78-0. 

 o2 



