CATALOGUE OF THE SERIltS ILLUSTRATIXG THE PROPERTIES 



OF MINERALS. 



By Wirt Tassix, 

 Assistatit Curator, Dirisioit of Mineralogy. 



INTRODUCTION. 



The wall cases on the west side of the Mineral Hall contain a series 

 of specimens, models, and labels illustrating and defining the several 

 characters or properties of minerals. Accepting the definition of a 

 mineral to be a definite chemical compound occurring in nature, which 

 is usually capable of assuming a crystalline form when in the solid state, 

 the subject-matter, consisting entirely of the labels used throughout 

 the series, may from this definition be made to fall under two heads: 



I. Chemical mineralogy, which treats of those properties relating to 

 chemical composition or atomic structure of a mineral, and tlie chemi- 

 cal relations of the several kinds of minerals. 



II. Physical mineralogy, which treats of those properties relating to 

 form or molecular structure of a mineral, and the action of the various 

 physical forces upon the several kinds of minerals. 



SYNOPSIS OF ARRANGEMENT. 



I. CHEMICAL MINERALOCIY, 



The elements: combination; types of minerals,- variations in composi- 

 tion; relation of water to composition; relation of water to physical 

 properties; relation of composition to physical properties. 



II. PHYSICAL MINERALOGY. 



A. Properties relating to form or molecular structure: The crystal; 

 crystallographicaxes; crystal form; crystal systems — isometric, tetrag- 

 onal, hexagonal, orthorhombic, monoclinic, and triclinic; symmetry and 

 the thirty-two types; compound crystals; imperfections of crystals; 

 pleomorphism, isomorphism; pseudomorphs; crystalline aggregates. 



P>. Characters relating to cohesion and elasticity: Cleavage; gliding, 

 pressure, and separation ])lanes; fracture; hardness; tenacity. 



C. Characters depending upon mass or volume: Specific gravity. 



D. Characters relating to heat, magnetism, and electricity: Heat, 



magnetism, electricity. 



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