998 REPORT OF NATIONAL MUSEUM, 1895. 



GENERAL ARRANGEMENT. 



The systematic series is divided into two general classes — native 

 elements and compounds of the elements. The compounds of the ele- 

 ments are further divided and grouped under certain heads according 

 to, and which take their names from, their more negative constituents 

 as follows: Compounds 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 sulphantimonides; also sul- 

 phosalts. Oxygen compounds, including oxides and the oxygen salts, 

 borates, aluminates, ferrites, chromites, manganites, uranates, carbon- 

 ates, silicates, titanates, columbates, tantalates, nitrates, vanadates, 

 phosphates, arsenates, antimonates, sulphates, chromates, tellurates, 

 molybdates, and tungstates. Compounds of organic origin, including 

 salts of organic acids and hydrocarbon compounds. 



Each of these classes is further separated into groups, the minerals 

 included in any one group being such as are related in the miiiior 

 details of chemical composition and physical properties. Each of these 

 groups is preceded by a general group label giving the class to which 

 it belongs, the group name, the minerals composing that group together 

 with their chemical composition, system of crystallization, and a short 

 description of the occurrence, association, and characteristic form of 

 each member of the group. The following label will serve to give a 

 clearer idea of this arrangement: 



Tungstates, 



Wolframite Group. 



Wolframite, (Fe,Mn)W04 Monoclinic. 



Hiibnerite, MnW04 Monoclinic. 



Wolframite. — Chiefly ferrous tiingstate, with some manganese. It occnrs in irregu- 

 lar lamellar, coarse divergent columnar, and granular masses, and in crystals, com- 

 monly tabular. Color and streak nearly black. Wolframite is often associated 

 with tin ores, and with quartz carrying bismuth, scheelite, pyrite, galena, sphaler- 

 ite, etc. 



Huhnerite. — Chiefly manganese tungstate, with some iron. It occurs in bladed 

 forms and massive in quartz, and with alabandite, rhodonite, scheelite, fluorite, and 

 apatite. Color brownish red. hair brown to nearly black. Streak yellowish brown. 



Following the group label, arranged in order from left to right, are 

 the several members of the group, selected to illustrate as completely 

 as possible their occurrences, associations, and variety in form and 

 color. Each specimen is mounted upon a block, in front of which is a 

 small label giving the name of the species, the minerals associated 

 with it in that particular specimen, if any, its locality, catalogue num- 

 ber, and from whom and how received. 



The several groups are placed in regular order in the cases, and each 

 case carries a case label giving the name of the class to which its con- 

 tents are referred. In the upper left hand corner of each case is a 

 numeral followed by an arrow, which serves to indicate the sequence 



