JADE. 



Jade is a term applied in general to a 

 tough, fibrous mineral of a greenish col- 

 or having the composition of a pyroxene 

 or amphibole. Until recently the miner- 

 al was supposed to form a single spe- 

 cies, but it is now known that at least 

 two species are grouped under this title. 

 One of these is a form of pyroxene and 

 is known as jadeite, the other is a form 

 of amphibole, and is named nephrite. 

 Further the term is often used to include 

 any tough green stone having a hard- 

 ness between 6 and 7 and taking a good 

 polish, since such rock or minerals 

 are often carved by people who use 

 true jade. Jadeite is a mineral of defi- 

 nite composition, it being a silicate of 

 soda and alumina. The percentage 

 composition of pure jadeite is — silica 

 59.4 per cent, alumina 25.2 per cent 

 and soda 15.4 per cent. Its hardness 

 is a little below that of quartz or be- 

 tween 6.5 and 7, but its extreme tough- 

 ness makes it often seem harder than 

 this. It is a rather heavy mineral, its 

 specific gravity being 3.35. In color it 

 varies from nearly white to nearly emer- 

 ald green. The white varieties some- 

 times contain spots of bright green sup- 

 posed to be due to chromium. The min- 

 eral does not crystalHze, but is known 

 from its optical properties to be either 

 monoclinic or triclinic. It does not oc- 

 cur transparent, but has a peculiar trans- 

 lucency or subtranslucency not unlike 

 that of horn or fine porcelain. It has a 

 fibrous to granular structure readily seen 

 under the microscope and a splintery 

 fracture. It is very tough. Jadeite 

 fuses readily before the blowpipe to a 

 transparent, blebby glass and colors the 

 flame yellow, thus differing from 

 nephrite which is almost infusible. The 

 term chloromelanite is applied to a 

 dark-green to black jadeite containing 

 considerable iron. 



Objects of jadeite carved in prehis- 

 toric times are found abundantly in 

 Europe, Asia, America and Africa, but 



only a few of the original localities 

 whence it was obtained are now known. 

 The most important locality known at 

 the present time is in Upper Burma in 

 the vicinity of Monoung. The jadeite 

 occurs in bowlders embedded in a red- 

 dish yellow clay in the valleys of trib- 

 utaries of the Dschindwin river. The 

 bowlders are mined by digging shallow 

 pits after the fashion of the Burmese 

 miners, as many as a thousand men oft- 

 en being employed in this work. The 

 miners break the bowlders by heating 

 and when pieces of quality suitable for 

 cutting are found they are either laid 

 aside to sell to caravans which come_ to 

 the mines for this purpose from China 

 or are turned over to native artisans 

 who reduce them to desired shapes bv 

 sawing them with a saw made of steel 

 wire strung on a bamboo bow. The ja- 

 deite from this locality is commercial- 

 ly distributed all over China, where it 

 is held in high esteem and commands a 

 high price. Bauer states that he saw a 

 piece containing less than three cubic 

 feet which was valued at $^0,000. The 

 jadeite of milk-white color is that most 

 highly esteemed, although that with 

 bright green spots is also considered of 

 superior A^alue. 



Nephrite is a variety of amphibole 

 much resembling jadeite in color, hard- 

 ness and texture. It is, however, of 

 somewhat lower specific gravity than 

 jadeite, raneing as it does from 2.96 to 

 3.1. and it fuses with much greater dif- 

 ficultv. Under the microscope a sec- 

 tion shows a finely fibrous character dif- 

 fering from the broad fibers or gran- 

 iles of jadeite and the optical characters 

 throughout are those of an amphibole 

 rather than of a pyroxene. In com- 

 position nephrite is a silicate of calcmm 

 and magnesium, having the theoretical 

 percentages, silica 57.7. magnesia 28.9 

 and lime 13.4. A little alumina, iron 

 and soda are often found combined 

 with the above. Nephrite has the glist- 



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