390 
Lime, owing to some Calcites which the microscope had pre- 
viously discovered. 
On placing the pulverised rock into a “ Thoulet’s” solution 
of 3'202 specific gravity, the ore was gradually precipitated, 
and on analysis of that precipitate, the presence of Iron 
Pyrites was detected with slight traces of Antimony, Copper, 
and Zinc. The chemical and microscopical examinations 
which followed established the composition of the rock as 
follows :—Quartz, Topaz, Iron Pyrites, Calcite, Titanites, and 
Apatite (?) of which the first two form the leading, and the 
remainder the less important constituents. The base of the 
Topaz, as ascertained by analysis, appears, in the microscopie¢ 
slides under their proper magnifier, as an aggregation of 
colourless and irregularly formed crystalline grains not above 
0:02 min. measurement. Every now and then—especially in 
the vicinity of the crystals of iron pyrites, the basic Topaz 
partakes of a more fibrous texture, gaining thereby an 
appearance which very closely assimilates with the denser 
whitish Topaz referred to below. The very small crystals, 
already alluded to, as having been observed in the fractures 
of the rock itself, sometimes enclose such fibrous Topaz, and 
they are frequently coated by a whitish mineral, which on 
account of its granular composition renders the inner or 
enclosed crystals necessarily less clear, but opaque. It has 
been impossible for me, at present, to classify these small 
crystals under any distinct system. Itis likewise not possible 
to declare same as “ pseudo-morphic”’ as there are no grounds 
for such an assumption. On the other hand, they may be 
accepted as imperfectly formed, minimised crystals of Topaz 
—amucroscopic Pycnite (?)—as composed of very minute fibrous 
crystals, and that their want of clearness is due to those in- 
crustations. It remains now only to be observed, that within 
those minute crystals, grains or specks occur, which exhibit 
vividly coloured polarising colours (also of Topaz) as well as 
irregularly formed particles of iron pyrites. 
The Quartz occurs in the basic mass of the rock in the form 
of crystalline grains or aggregations from 0:06 to several 
mins. in measurement. To judge from the very regularly 
developed form—six sided—of some of these crystals, and _ 
their behaviour, when crossing each other’s positions, the well- 
known Dihexadron would most likely be their form under 
that system, if accompanied by the narrow column sides 
which are so frequently observed when embedded in Quartz- 
Porphyries. On magnifying these transparent and polarising 
crystalline aggregations 400 times their original size, they 
exhibit frequently those well-known vesicular openings 
filled with fluids. Fluids, because, they do not appear 
to consist of carbonic acid, as is sometimes the case, 
