NOTES ON ASBESTOS AND ASBESTIFORM MINERALS. 



By George P. Merrill, 



Curator of the Department of Geology. 



The investigations detailed below are an outgrowth of an attempt at 

 classifying and labeling tlie "'asbestos" collections in the economic 

 series of the geological department of the National Museum. The 

 results seem of sufficient interest to warrant immediate publication, as 

 the final handbook' of which they were designed to form a part may 

 yet be delayed some months. 



Without going too deeply into a discussion of the origin of the name 

 "asbestos,'' and the causes which led to its present loosely-defined min- 

 eralogical significance,^ it may be said that as commercially used the 

 name now covers at least four distinct minerals, having in common 

 only a tibrous structure and more or less fire- and acid-proof properties. 

 These minerals are (1) monoclinic amphibole (treniolite), (2) serpentine 

 (amianthus), (o) anthophyllite, and (4) crocidolite. Of these, tremolite 

 and serpentine have long been recognized in fibrous forms, and are as 

 a rule readily distinguishable from one another by the silky fiber and 

 greater flexibility of the last named. Asbestiform crocidolite is well 

 known to most mineralogists, though, so far as the present Avriter is 

 aware, the South African locality is the only source of the mineral in 

 commercial quantities. That the fibrous form of anthophyllite is also 

 sufficiently common to be commercially used as asbestos, seems not so 

 well understood, though the leading text-books on the subject^ all 

 mention the mineral as sometimes occurring in fibrous forms resembling 

 asbestos. That a lack of discrimination between fibrous anthophyllite 

 and the true tremolite asbestos should exist is not strange, since to 

 the unaided eye they are often iu every way alike, and it is only by 

 microscopic or chemical means that the true nature of the mineral can 

 be made out. 



'The Nonmetallic Minerals, now in process of preparation. 



'^See "Some Misconceptions concerning Asbfstns," by J. T. Donald and A. II. 

 Chester, in the Eng-. and Min. Journal for March 18, April 1, and June 10, 1893. 



^See Dana's System of Mineralogy, latest edition, and Hintze's Uandbuch der 

 Mineralogie. 



Proceedings of the United States National Museum , Vol. X VIII— No. 1066. 



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