76 GEMS OF AUSTRALIA. 



as it prepares the mind to grasp and retain certain leading 

 principles, whicli it is essential for the mineralogist, or the 

 " prospector" (as the man who searches for minerals ia christened 

 in Australia) to remember. 



Disti7ietion between Geology and Mineralogy. — Although the 

 two sciences are so intimately connected, that the two terms are 

 often used synonymously, there is ia fact a wide distinction. To 

 give definitions in the simplest form of words, — Geology treats 

 of the structure of the earth, and the changes it has undergone 

 from its creation out of chaos to the present time ; Mineralogy 

 describes in detail the various component parts or substances 

 of which terrestrial matter is formed, and declares the forms, 

 properties, and qualities of those substances. Eor instance, 

 the geologist, — in passing by a deep railway- cutting, or descending 

 the shaft of a mine,- — possibly finds a stratum of rounded pebbles ; 

 and knows that they have acquired that form by friction, as they 

 have been driven over rocks, or against each other, by moving water 

 in some bygone age. The mineralogist examines the component 

 parts of the stratum, and finds that the pebbles are composed 

 of granite, quartz, greenstone, &c. Again ; the geologist observes 

 that a deposit of a blue stone or lava, many feet in depth, has 

 overlaid thick beds of sedimentary rocks, or a drift of pebbles and 

 gravel (the washdirt of the gold-miner), and knows that the 

 lava was once in a molten state, and ejected from a volcano at 

 some period of the world's history. The mineralogist observes 

 the character of the lava ; he finds it is of that specific kind 

 called " amygdaloidal" basalt, from the almond-shaped cavities in 

 the mass ; and he possibly finds some crystals of olivine in those 

 cavities. The mineralogist then declares the value of the basalt, 

 for its toughness and durability as a building-stone or metal for 

 roads, and of the olivine, as an ornamental gem, known as chryso- 

 lite. In short, it is the object of Mineralogy, as well observed by 

 Professor Ansted, to describe the form, the internal structure, the 

 chemical composition, the physical properties, and the uses to man, 

 of all those natural material productions or substances, which are 

 not organic, i.e., which do not possess vitality, or the powers of 

 reproduction, like animals and plants. 



Physical cTiaracter of minerals. — Mineralogists distinguish 

 these various inorganic substances, one from another, by several 

 means : — 



1. By chemical analysis. — This is the most elaborate and the 

 most accurate test, as it determines -nith certainty the component 

 parts of each specimen examined ; but, as the mineral must be 

 partially, if not wholly destroyed, it is more rarely resorted to 

 by the mineralogist as a test for gems or precious stones. 



