PREFATORY NOTE. 



The accompanying handbook and guide is an outgrowth of the work 

 of installing and labeling the collections of the economic section of the 

 Division of Physical and Chemical Geology. The term nonmetallic, 

 as used, includes those minerals which, as here exhibited, are utilized 

 in other than metallic forms. The collections, comprising as now 

 arranged, some 2,500 specimens, include therefore some materials 

 which like the iron oxides may be utilized as ores of metals. As 

 such they have already been considered in Bulletin No. 42, under the 

 title A Preliminary Descriptive Catalogue of the Systematic Collec- 

 tions in Economic Geology and Metallurgy, by F. P. Dewey. The 

 collection of building and ornamental stones which might perhaps be 

 included herewith has been also the subject of a special handbook 

 published in the Annual Report of the National Museum for 1886, 

 and entitled The Collection of Building and Ornamental Stones in the 

 United States National Museum: A Handbook and Catalogue. By 

 George P. Merrill. 



It is scarcely necessary to remark that in the preparation of this 

 work the curator has been hampered by a great dearth of information 

 on certain subjects and burdened with a superabundance on others. 

 Certain materials, such as the coals, phosphates, limes, and cements, 

 would each require a volume, and necessarily must be very imper- 

 fectly treated here. In such cases the curator has aimed to give as 

 brief and concise an abstract as the requirements of a handbook 

 would permit, and make up for the deficiencies in the bibliography. 

 In other cases the subjects are treated as fully as the knowledge at 

 hand will allow. In describing occurrences the aim has been to give 

 in detail one or two fairly typical deposits, referring to others more 

 briefly. Naturally the preference has been given to American mate- \ 

 rials. Statements as to prices and annual production are quite unsatis- 

 factory and of very temporary value at best. But little space has 

 therefore been devoted to this branch of the subject. Technical, 

 chemical, and crystallographic points have been but lightly touched 

 upon, such being already covered by existing literature. Only such 

 statements as to hardness, color, etc. , are given as it is thought may 

 be of value in rough preliminary determinations. 



The satisfactory installation and classification of collections of this 

 nature are matters of no inconsiderable difficulty. As the materials 



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