128 GUIDE TO THE AUSTRALIAN MUSEUM. 



The analogy between these and the rocks of our planet is 

 carried out in all the details of their structure, some beino: 

 fragmentary like our breccias, some oolitic, some granular like 

 sandstone, while others exhibit structures peculiar to some 

 volcanic rocks, being vascular, globular, vitreous, &c., leaving no 

 doubt that they are the debris of a small disintegrated satellite 

 of the earth, 



iy._ORNAMENTAL COLLECTION. 



With the exception of some nicely cut vases of Fluor Spar, 

 placed in a special case at the entrance of the room, one ornamen- 

 tal vase of Porphyry, and two of Serpentine exhibited by 

 themselves, and some Marble and Serpentine slabs along the 

 wall, most of the ornamental stones are placed in an upright 

 case standing opposite the entrance. 



Among the stones or non-metallic minerals the princi- 

 pal mineralogical specimens represented are Calcite and 

 Aragonite (Carbonate of Lime) represented by Slabs of 

 Onyx, Marbles, and a small " sarcophagus " of rare antique 

 marble. The material from which some candlesticks and vases 

 exhibited under Catalogue numbers 2243 to 2249 are made, 

 although known as alabaster is not ti'ue alabaster, which is a 

 variety of Gypsum (sulphate of lime), but is a variety of concre- 

 tionary marble analogous to the stalactites of limestone caves. 

 A variety of true Alabaster (another sulphate of lime) also called 

 Satin Spar is represented by a necklace and cross under No. 2242. 

 The name of Satin Spar, as well as Alabaster, has been 

 given to varieties of both Sulphate and Carbonate of Lime, a speci- 

 men of the latter being in the general collection under No. 199* 

 Silicic Acid or Silica inclades here the numerous ornamental 

 varieties of quartz, and impure quartz of different colors sacli as 

 Agate, Onyx, Jasper, Chrysoprase, &c. In order to mark a 

 striking distinction between the different varieties of quartz, 

 which are considered as gems, such as Amethyst, Smoky Quartz, 

 Cairngorm, Citrine Quartz, &c., and the other gems, among 

 which are the most precious stones, the large collection of cut 

 amethysts has been placed in this case. 



