OCCURRENCE OF PRECIOUS STONES IN N.S.W. 269 
It may be noted in general that stones that will not scratch glass 
(opal excepted) are useless as gems. Also that stones that fuse 
easily before the blowpipe are as a rule worthless. 
I would repeat that these notes are not intended to replace the 
directions found in so many miners’ handbooks, but rather to 
supplement what they deal with. There is no difficulty in dis- 
tinguishing gems when instruments and scientific apparatus are at 
hand, and these notes may be of service when such help is not 
available. 
EXPLANATION OF PLATES. 
Plate XIII. 
1—Two crystals of topaz from New En ngla land. Natural size. The 
lue-green, more pronounced iowas one end, in the stone. The pleo- 
chroism is however very marked. This specimen is so eveuly abraded 
that not a trace of the basal cleavage can be seen, rather a remarkable 
feature for so — a vais with so perfect a cleavage. The “ Maxwell. . 
Stuart” topaz, sai the largest cut precious stone known,”’' weighs 
1475 grains. The specimen: — should cut into an excellent stone 
to turn the scale at 1800 grai 
Fig. 2—The crystal shewn on the same plate is characteristic of the 
habit of the larger topaz, that are found over the granitic areas of the 
New England. Prismatic and pyramidal faces are well developed. But 
the brachydomes f are so prominent as to give a wedge-shape to the 
crystal when it stands on the traces of the basal clea vage. This speci- 
men weighs 3,063 grains. It is marred by several feathers, so that the 
stone could not be cut into one large gem. a, brachydomes; b, pyramid; 
&, ¢, prisms. 
Fig. 3—A crystal of topaz found in a granitic detritus, Oban, New 
England. Natural size. This fine a weighs 6,839 grains and has 
a decided blue tint with a cloud of amber-brown, filling about one-fourth 
of the specimen towards the centre. th basal cleavage in this example 
is perfect. The prisms and pyramids are striated. The wedge-shaped 
Soteeagd of the crystal is due to the great development of the brachy- 
omes, 
Plate XIV. 
Fig. 1—Topaz shewing perfectly water-worn and rounded specimens. 
Natural size. Vegetable Creek, New England. 
i oe i 
2 Min, Mag. Vol. 111., p. 95. 
