175 



ROCKS. 



The collection o£ rocks is a very large one, but very little space 

 is at present available for its exhibition. The small series now on 

 view must, therefore, be regarded as temporary only. A separate 

 guide to the igneous rocks of New South "Wales will be issued 

 shortly. 



The division at present adopted is a three-fold one, viz., 

 'New South Wales, Inter-State, and Foreign. 



The primary division is into igneous and sedimentary. The 

 igneous rocks will then be grouped geograjjJiicaUi/. In this w^ay 

 those from the New England Table-land, or from the Hawkesbury 

 formation, will be found together. The igneous rocks from any 

 given district will be arranged according to the table on page 177. 

 The sedimentary rocks will be arranged according to their 

 geological age (see page 178). 



Barrier Range. — The rocks here constitute a complex group igneous Eocks. 

 of igneous and sedimentary origin, of the greatest geological ^- S- Wales, 

 age, that have undergone intense metamorphism. They consist Case 145. 

 principally of gneisses and schists. 



8109 is a fine specimen of staurolite-mica-schist, and 10111a of 

 cyanite-mica-schist. 



Western District. — Trachytes, basalts, and tuffs from the CaseS 

 Canoblas, Orange — an old volcanic centre. \4iQ 147. 



Northern District. — Crystalline acid rocks. Granites and Oase 142. 

 porphyries from New England, &c. 



Northern District. — Hemi-crystalline, glassy, and tufr rocks. (JasC 143, 

 A rhyolite (an old lava floAv) from Paddy's Hill, Raymond 

 Terrace is exceptionally fine. Large blocks of it are placed on 

 the top shelf of case 147. By means of these and of the large 

 transparent slice shown here the visitor wdll readily distinguish 

 the flow-structure produced when the rock was a stream of viscid 

 lava. Yery fine rhyolite glass occurs in the Tweed River, and 

 in the Carboniferous Strata of the Copeland and other districts. 



Northern District. — Basic rocks. Case 144. 



8961, Elsmore ; a magnificent specimen of basalt glass or 

 tachylyte. — This rock occurs at the sides of a basalt dyke or 

 sheet, where it has cooled quickly. It is not a common rocli, and 

 is usually a very thin edging only. A similar tachylyte occurs at 

 Bowen Park, near Cudal. 



