MR. J. T. HOTBI.ACK ON PRECIOUS STONES. 
25 
The lapis lazuli of jewellers should be an opaque but rich azure- 
blue. It is not infrequently found with iron pyrites disseminated 
through it, when it has the appearance of being spotted with gold. 
This stone was well known to the ancients, and is still extensively 
used for studs, pins, and other articles of jewellery, but it is most 
used for vases, mosaic work, and to ornament furniture. Many 
fine examples exist in Continental Catholic Churches in pillars and 
adornments of the altars, shrines, &c. 
This stone, when ground to powder, is the true ultramarine 
once so valuable, but now nearly superseded by a manufactured 
substitute at not a hundredth part of the cost. 
Jade or Nephrite. 
This stone is, I think, never found crystallized. Its composition 
is very variable, so much so that it is not classed as a distinct 
mineral. Its hardness ranges from 6 to 7, its S.G. from 2.9 to 3.1, 
and I find its composition variously stated as under : 
Silica 
50.5 
58.9 
Magnesia 
. . . 
31.0 
22.4 
Lime 
— 
12.3 
Alumina 
10.0 
1.3 
Protoxide of Iron ... 
... 
5.5 
2.7 
Water 
... 
... 
2.8 
0.3 
Though seldom used for purposes of jewellery in this country, 
through the whole of Asia jade is very highly esteemed. The 
colour most valued is a pale greenish grey, and good specimens 
fetch very large prices. 
Jade is found in China, Egypt, Corsia, and in other places in the 
old world, and in Australia and New Zealand ; the natives of the 
latter, and other islands, used it for the heads of axes and other 
weapons, grinding it to a sharp cutting edge with a fine polish. 
This New Zealand jade was said at one time not to be the same as 
the stone so highly valued by the Chinese mandarins for their 
buttons of high office, but I think it is now admitted that the one 
cannot be distinguished from the other. 
Turquoise. 
This is another stone never found crystallized, but ■while jade is 
sometimes found in rather large masses, turquoise is, I think, 
