95 



The Newcastle Coal Measures are the most important ; they 

 attain a great thickness at Lake Macquarie. Of the various 

 seams of coal (see section, page 94) the most important is the Bore- 

 hole Seam ; it is from 8 to 21 feet thick, and is the one worked at 

 the principal collieries. Some of the upper seams have been 

 worked. 



Specimens of coal from various collieries, in some cases dJ^se 74. 

 accompanied by complete analyses, are exhibited. These include 

 samples from the Borehole, Burwood, Yard and 2-foot seams. 



Coal from the Illawarra, Miltagong, Blue Mouutain, Dubbo, (Jase 75. 

 jSTamoi Eiver and Tweed Elver districts. 



A seam of carbonaceous shale occurs at "Wilson's Downfall, pium'bago. 

 It is of very poor quality. 



• MISCELLANEOUS MINERALS OF COMMERCIAL 



VALUE.* 

 Hydrous sulphate of alumina and potash : a massive mineral Case 76, 

 often found in large deposits. It is used as a source of alum. Alunite. 



Alunite has been largely mined at Bulladelah, in the Stroud 

 District. Specimens are exhibited, ranging in colour from rose- 

 pink to almost chalky-white. Several complete analyses are 

 given. 



4216, a rose-red variety cut and polished. 



9546, HalloysUe, hydrous silicate of alumina found associated 

 with the alunite. 



Natural alums are of common occurrence, occupying cracks Alran. 

 or lining cavities in the Hawkesbury sandstone and other rocks. 

 They do not occur in sufficient quantity to be of commercial 

 value. Zinc has sometimes been detected in them. 



3076, Mount "Wingen ; a hydrous sulphate of alumina with 

 sulphur. 



Magnesia alums from Wallerawang, Mount Victoria, Shoal- 

 haven, Capertee, Burragorang. 



* For cement, sec jsage 135. 



