890 Transactions.—Geology. 
Opal, Si, H, or Si H*.— The more valuable varieties are not known in 
New Zealand, but the inferior qualities are of common occurrence. 
Hyalite is mentioned by Dr. v. Haast as occurring in small masses, 
lining cavities in the voleanie rocks of Snowy Peak and the Malvern Hills 
(Jurors' Rep. N.Z. Ex., 1865, p, 256), and again in a few localities in the 
voleanie rocks of Banks Peninsula (Trans. N.Z. Inst., vol. xi., p. 511), and 
is also mentioned by Professor Liversidge (Trans. N.Z. Inst., vol. x., p. 496) 
lining eavities in the vesicular grey trachytes of Bell Hill, Dunedin. 
Common Opal and Semi-opal are mentioned by Dr. v. Haast (Jurors’ 
Rep. N.Z. Ex., 1865, p. 256) as filling small cavities in the quartz por- 
phyries of the Malvern Hills and Mt. Somers, and last year I obtained from 
the drift of Owharoa a specimen which is of a pure milky-white colour. 
Wood Opal (Silicified Wood) is very common where siliceous rocks are 
decomposing as at Petrifying Gully, Mount Somers. It is mentioned by 
Dr. v. Hochstetter (New Zealand 1868, Eng. ed., p. 96) in the tuffs and 
conglomerates of Coromandel, and by Dr. Haast (Juror's Rep. N.Z. Ex., 
1865, p. 256) from many localities in Canterbury. 
Pitch Opal.—A specimen from Dunstan is described by Prof. Liversidge 
(Trans. N.Z. Inst., vol. x., p. 496) as follows :—'* Brown, variegated, light 
and dark shades. Hardness about 6. When heated in closed tube gives 
off water, blackens, and emits empyreumatie odour; the condensed water 
has an acid reaction, and on evaporation leaves a carbonaceous residue 
which blackens on ignition; breaks with a well-marked conchoidal frac- 
ture; contains iron.” There are two specimens of this mineral in the 
collection of the Colonial Museum—one from the Harper Hills, and the 
other from the Rakaia Gorge. 
Opal-jasper.— There is in the collection of the Colonial Museum a speci- 
men of opaline quartz with jasper, from the trachyte tufa of Portobello, 
Otago, which forms a very pretty ornamental stone. The predominating 
colours as described by Prof. Liversidge (Trans. N.Z. Inst., vol. x., p. 496) 
are red-brown, blue-grey, and opal-white. 
Siliceous Sinter.— Deposits of this class are found surrounding several of 
the thermal springs, and have been well described by Dr. v. Hochstetter 
(New Zealand, 1863, Eng. ed., pp. 398, 412). He says, in speaking of the 
siliceous deposits of Orakeikorako: ‘The sediment of this, like all the 
surrounding streams, is siliceous; the recent sediment is soft as gelatine, 
gradually hardening into a triturable mass, sandy to the touch, and finally 
forming, by the layers deposited one above the other, a solid mass of rock 
of very variable description at different places both as to colour and struc- 
ture. Here it is a radiated fibrous or stalky mass of light brown colour ; 
there a chalcedony hard as steel, or a grey flint ; at other places the deposit 
