19 



Hydrated phosphate of alumina: Thin veins of turquoise occur Case 49. 

 iu an indurated shate near Bodalla. 5782 shows the mode of Turquoise, 

 occurrence in veins. The deposit has not as yet proved of 

 commercial value. 



'Por turquoise from Victoria and Queensland, see case 78; and 

 for other phosphates of alumina, case 102. 



The gem variety of beryl : Silicate of alumina and berylla. Emerald. 

 Eor beryl in general, see case 100. This mineral contains the 

 rare element glucinium (beryllium). It is frequently associated 

 with tinstone in New England (7949, 1988, 1616, 7937, 5355, 

 in case 64), especially from The Grulf. It is one of the 

 minerals (see above under Topaz) frequently found in granite. 

 Emmaville is the only locality in New South Wales where 

 emeralds of marketable quality have been found. The cut stones 

 exhibited represent some of the best. It will be seen that the 

 colour is rather pale. The mode of occurrence in granite is 

 well shown by 6918, 2122, 2180. The granite consists of 

 cream-coloured felspar, with quartz, black mica, and tinstone, 

 and contains well-formed emerald crystals embedded in it pro- 

 miscuously. The six-sided prisms of beryl are very characteristic. 

 2122 shows several such, both Jongitudinally and in transverse 

 section. Beryl is harder than quartz (H=nearly 8) and will 

 therefore scratch glass readily. The density is low, but it 

 will generally sink in heavy liquids (see page 15) diluted so as 

 to just permit quartz to float. Beryl never has the pyramidal 

 terminations of quartz. A large block, showing several emeralds 

 in situ, will be found in case 128. 



Simple crystal of Beryl. Prism with basal plane. 



