220 REPORT OP NATIONAL MUSEUM, 1901. 



The most striking of the objects here brought together were ;t 

 small but very perfecl octahedral crystal of a diamond from South 

 Africa; a fine large mass of native arsenic from the Hartz Moun- 

 tains, Germany; a like mass of antimony from New Brunswick; beau- 

 tiful examples of wire and moss gold from California; branching 

 crystals of silver and copper from the Lake Superior mines; thin films 

 of native lead from Sweden; tellurium from Nevada; iridosmine from 

 the Pacific coast of Oregon; native iron from Greenland, and a tine 

 water-worn nugget of platinum weighing 444 grams from the Nijni 

 Tagilsk district, Russia. 



There was also a case of striking concretionary forms, including 

 examples of the so-called "kugel" or orbicular granites from Sweden, 

 Finland, and Rhode Island, and of the septarian concretions of clay 

 ironstone from Weymouth, England; New York; Kansas, and other 

 localities. Examples of the individual specimens are shown on Plates 

 60 and 61. 



II.— DIVISION OF MINERALOGY. 



The exhibit of the Division of Mineralogy was arranged with the 

 following objects in view: To make as attractive a display as possible 

 with the material and space available; to illustrate methods of arrange- 

 ment and installation used by the division; to be self-explanatory and 

 complete in itself. In the carrying out of this a systematic arrange- 

 ment of minerals was planned which should show specimens of the 

 more important minerals and their arrangement in accordance with 

 the genera] scheme of classification, as outlined in the label, a transcript 

 of which is given below: 



V SYSTEMATIC ARRANGEMENT OF MINERALS. 



Tlie chemical composition of the mineral determines its position in tin- several 

 classes. These classes, which are arranged in accordance with certain chemical laws 

 having the periodic arrangement, of the elements as a basis, are made up of those 

 minerals having the same dominant negative chemical radical from which the class 

 name is derived, as sulphide, silicate, etc. The whole is divided into two general 

 groups — native elements and compounds of the elements. The compounds of the 

 elements are further divided and grouped under certain classes according to, and 

 which take their names from, their more negative constituents, as follows: Com- 

 pounds of the halogens, fluorides, chlorides, bromides, and iodides. Compounds of 

 sulphur, selenium, and tellurium; also arsenic and antimony, including sulphides, 

 selenides, and tellurides; arsenides, antimonides, sulpharsenides, and sulphantimo- 

 nides; also sulphosalts. < >xygen compounds, including oxides and the oxygen salts, 

 borates, aluminates, chromites, ferrites, manganites, plumbates, arsenites and anti- 

 monites, selenites and tellurites, carbonates, silicates, titanates, columbates and tan- 

 talates, nitrates, vanadates, phosphates, arsenates and antimonates, sulphates, 

 selenates and tellurates, chromates, molybdates and tungstates, iodates, and uranates. 

 ( (impounds of organic origin, including salts of organic acids and carbon compounds. 



