3. DESCRIPTIVE CATALOGUE OF THE COLLECTIONS. 



The arrangement of the gem names in this catalogue is alphabetical 

 throughout so far as practicable. Under each mineral or gem is 

 given in tabular form some of the more striking qualities of a descrip- 

 tive or determinative nature, followed by remarks on the mode of 

 occurrence and such other miscellaneous information as it is thought 

 will be of value. In the catalogue proper the material is arranged 

 in the following order: Name, locality, cut, color, weight, measure- 

 ments, and catalogue number. The weights are given in the newly 

 introduced metro-carats. The specimens are listed by localities, 

 alphabetically, and under each locality are arranged in the order of 

 decreasing weights, except where several stones are described to- 

 gether, these being placed at the end of the list for that particular 

 locality. 



Adularia. — See under Feldspar. 



Agate. — See under Chalcedony. 



Alabaster. — See under Gypsum. 



Albite. — See under Feldspar (Moonstone). 



Alexandrite. — See under Chrysoberyl. 



Almandite. — See under Garnet. 



Amazonstone. — See under Feldspar. 



AMBER. 



Synonym .—Succinite. 



Composition. — A resinous substance, containing carbon, hydrogen, 

 and oxygen. 



Crystallization. — Amorphous. 



Color. — Yellow, orange-yellow, brown-yellow, or rarely red. 



Luster. — Resinous; transparent to translucent. 



Hardness. — 2.5; too soft for extensive use as a precious stone. 



Optical properties. — Mean refractive index 1.54; is isotropic ex- 

 cepting when in a condition of strain. 



Specific gravity. — 1.07; noticeably light. 



Amber is a poor conductor of heat and electricity, becoming elec- 

 trified when rubbed on cloth so that it will attract small bits of paper. 

 It can bo distinguished from imitations such as rosin and celluloid 

 by being less inflammable, though it burns readily with a rich yellow 

 flame, yielding an aromatic odor. Heated to 150° C. it begins to 

 soften and melts at about 250°. From most minerals it may be 

 distinguished by its extreme lightness and its solubility in alcohol. 



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