XxX. ROCK SPECIMENS. | 
Systematic arrangement according to the cpt 
; 

tion given in Cotta’s “Treatise of Lithology,” English 
translation,—Longmans, 1866. 
GENERAL SYNOPSIS. 
T. Iaxzous Rooks, products of absolute fusion. 
A.—Rocks poor in Silica, or Basic. 
(a.) Volcanic, e.g., Dolorite, Basalt, &e. 
(b.) Plutonic, e.g., Greenstones (Diabase, ke.) 
B.—Rocks rich in Silica, or Acidic. 
(a.) Volcanic, e.g., Trachytes. 
(b.) Plutonic, e.g., Granites. 
IL Meramorruic Crystatiine Scuists, products of 
heat (less than actual fusion), acting on Sedi- 
mentary Rocks, e.g., Gneiss, Mica Schist, &e. 
IIL Srepimentary Rocks, products of deposit, eg. 
Slates, Limestones, Sandstones, and 'Tufas. j 
TV. Rocks, probably of organic origin, e.@., ce 
ceous Rocks, Ironstones, Serpentines, &e. 
V. Rocks, composed of one mineral only, e.g., Qua 
Opal, &e. 
7 
I. IGNEOUS ROCKS. 
A.—Voleanic Basie Igneous Rocks. 
1. Doterire Group. 
Crystalline granular compounds of Labradorite ant 
Augite, with some Titaniferous Magnetic Iroi 
Ore. 
a. Common Dolerite. Maniototo Plain, Otago. 
b. Anamesite. Lyttelton Tunnel, Canterbury. : 
c. Porphyritic Dolerite. Lyttelton Tunnel, Canterbury: 
d. Vesicular Dolerite. Lyttelton Tunnel, Canterbury: 
