XV. — GEOLOGY AND MINERALOGY. 129 



Among the silicates are Figure-stone or Agalmatolite, and the 

 precious Jade, from both of which many Chinese ornaments and 

 other articles are made. Serpentine is the material of the carved 

 stone representing two serpents in allusion to the origin of the 

 name. Catlinite, a red clay rock, is the material of an Indian 

 pipe from Minnesota. 



Among the metallic minerals, a few are represented here by cut 

 ornaments ; namely, Rhodonite (Silicate of Manganese), Hematite 

 (Oxide of Iron), and Malachite (Carbonate of Copper). A larc^e 

 slab of Chalcedony from Italy, which has been framed as the top 

 of a table, is a good example of concretionary structure. 



In the most southerly of the cases on the right side of the room, 

 the rest of the ornamental and semi-precious stones, as well as 

 some models and imitations, rough uncut gems and samples of 

 gem sand, &c., are displayed. 



The space in the cases between the last mentioned and the last 

 case containing the minerals of the rare metals Yttrium, Cerium, 

 &c., is left vacant to receive provisionally, recently acquired 

 specimens. 



Against the south wall in the centre, rich blocks of Malachite 

 in geodes from Peak Downs, Queensland, are exhibited in a special 

 case, showing beautiful velvety crystallizations. 



Y.— COLLECTION ILLUSTRATING THE PHYSICAL 

 PROPERTIES OF MINERALS. 



This collection will be found useful to beginners and persons 

 unacquainted with the terms of Mineralogy. 



The form is first examined : (1) Geometric by crystallization. 

 Ex.: Rock Crystal or Quartz. (2) Geometric by contraction. 

 Ex. : Prisms of Basalt, Sandstone, &c. On the other hand, when 

 it is irregular, accidental or imitative, the form is indeterminate. 

 Some minerals exhibiting indeterminate forms may be crystalline 

 in structure, while others are not so. Of these forms examples of 

 concretions, incrustations and weathering are shown. A perfectly 

 rounded ball of sandstone from near Carcoar, is a rather puzzling 

 specimen. It has evidently been produced by a mechanical 



