BY W. F. PETTERD. 53) 
nodular masses in the Heazlewood Silver-lead mine with Siderite, 
which is commonly more or less stained with Chrome and Nickel 
oxides, Sphalerite, Galena, and other minerals. 
179. PLEONASTE (Black Spinel). 
The red or other coloured Spinels are not known to occur in 
the island, but the black variety is very abundant in tin-drift: it 
occurs as waterworn lumps, which are usually of small size: 
occasionally the crystallization is fairly defined. 
Weldborough; Blue Tier; Moorina; Branxholm ; Denison; 
Mount Maurice; Blyth River; Mount Cameron ; Hampshire 
Hills. This is one of the minerals termed “ Black-Jack” by the 
miners. 
180. PITTICITE (Arsenio-sulphate of Iron). 
Several small specimens of this rare mineral have been obtained 
near the Scamander River. 
181. PITCHSTONE (a variety of Obsidian). 
This remarkable and interesting substance is, as a rule, of an 
intensely black colour with a shining vitreous lustre and often 
extremely vesicular, the cavities being usually lined and occasionally 
completely filled with pure white Calcite or a magma of zeolitic 
material. It is but rarely that the species of Zeolite can be 
differentiated. It was met with in sinking a well in the township 
of Sheffield. 
Mr. A.W. Clarke, F.G.S., has made a careful micro-examination 
of this substance. The following is a copy of his report relating 
thereto (“The Geology and Paleontology of Queensland and 
New Guinea,” by R. L. Jack, F.G.S., &c., and R. Etheridge, jun., 
1892) :—“ No. 196, Sheffield (Tasmania), R. L. Jack’s collection. 
Colour black, vitreous. Glass with clear little white crystals. 
This is by far the most beautiful example of Pitchstone I have 
yet seen. ‘The crystals are olivine, and they are mostly preserved 
in equisitely regular forms in the glass: the faces oP (:001) are 
wanting. The section being a little thick and the glass very 
transparent, together with their high angle of refraction, enables 
one to recognise in these crystals many of the characteristic planes 
of the typical olivine crystal. In this rock students of micro- 
scopical crystallography have an opportunity of studying olivine 
in a perfect crystal form. Under the }-inch objective the olivines 
are seen to include glass with fixed glass bubbles. The glassy base 
carries nothing else but opaque dusty matter in spots, which is 
probably a darker glass nucleus fringed with dusty matter, in 
whose neighbourhood gas bubbles are commonly found. The 
glass has bubbles at tolerably regular intervals, and in one or two 
eases bubbles are strung out in shapes or outlines. The microlites 
are very small, and play no great part in the constitution of the 
