556 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



cheaply than the native product. It has been stated that the Burmese mines are not now 

 being worked, and if this is the case, the material which still comes into the native markets 

 must be part of an old stock. A large piece of amber, 11 J inches long, carved to represent 

 a duck, was taken from King Theebaw's palace at Mandalay, and is now preserved with the 

 Burmese regalia in the Indian Section of the Victoria and Albert Museum at South 

 Kensington. One of the presents given by the King of Ava to Colonel Symes, when on an 

 embassy to that country in 1795, was a box containing " amber in large pieces, uncommonly 

 pure." 



Amber-like resins are obtained in other countries also, one which appears to be very 

 rich in this respect being southern Mexico. The material is brought to the coast by 

 natives from some unknown locality in the interior, and is shipped as " Mexican amber." It 

 is of a rich golden-yellow colour, strongly fluorescent, and so abundant as to be used by the 

 natives as fuel. Details of the occurrence are quite unknown, and an examination of the 

 material itself is needed before it can be decided whether it consists of succinite or of 

 another similar resin. 



JET. 



Jet ("black amber"; German, Gagat, Agsteiii; French, jaM) is a variety of fossil coal 

 often worked for mourning ornaments and other articles. Material to be suitable for this 

 purpose must combine a number of characters, which are not, as a rule, associated in ordinary 

 coal. Thus it must be compact, dense, and homogeneous, characters which are expressed 

 by a perfect conchoidal fracture. It must contain no foreign matter, and specially no 

 iron-pyrites, a common impurity in coals. Moreover, the original internal woody structure 

 must not be retained, the preservation of the external form of the original stem or branch 

 from which the coal was formed does not, however, make the material unsuitable for the 

 purpose, but only emphasises its derivation from extinct trees. 



Material which is to be used for ornamental purposes must be free from patchiness, 

 and must be of a deep, pure black colour. Jet of a fine velvety black is most esteemed, 

 that showing a brownish shade being considered inferior. The lustre, which is of a 

 somewhat pronounced greasy kind, should not be too feeble and should be considerably 

 enhanced by polishing ; material with only a dull, glimmering lustre is quite worthless. 

 Finally, the substance must be tough enough to be cut with a knife, worked on the lathe, 

 filed or ground in the usual manner, and sufficiently hard to stand a reasonable amount of 

 wear without being damaged. The hardness of genuine jet varies between 3 and 4. 



Like all varieties of coal jet is perfectly opaque; the specific gravity is 1'35; the 

 specimens which are said to float on water are, therefore, probably porous. When heated 

 before the blowpipe the material easily ignites, being strongly impregnated with bituminous 

 matter. It burns for a time with a very smoky and sooty flame, giving off" an unpleasant 

 odour, and leaving behind a shining, porous, coke-like residue. Like all substances of 

 organic origin jet is a very poor conductor of heat, and hence feels warm to the touch, 

 this feature being especially noticeable in comparison with black minerals or with glass, and 

 serving to distinguish jet from these substances. 



