282 ASBESTOS JXP ASBESTIFORM MINERALS— MERRILL, vol. xviii. 



In the aocomi^a Dying" table (pages 291 and 292) i have brought together 

 all the analyses of the above noted asbestiforni minerals that have 

 been made either by R. L. Packard or myself in the department 

 laboratory, as well as sncli others as can be compiled from available 

 literature. It will be seen that out of the 24 analyses made by our- 

 selves, 12 are anthophyllite, 7 asbestiforni tremolite, and 2 uralitic 

 augite. This statement must not, however, be accepted as conveying 

 the idea that anytbing like the same proportions would hold in another 

 series, since only such samples were selected for our analyses as had 

 not been already satisfactorily determined. In all cases the optical 

 and chemical determinations agree, the mineral giving extinctions 

 parallel with the axis of elongation proving to be anthophyllite, and 

 that with inclined extinctions, tremolite (asbestos) or uralitic augite. 

 This result was not wholly exi)ected. since it was thought that possibly 

 some might be amphibole anthophyllite, /. c, a mineral with the com- 

 position of anthophyllite, but monoclinic in crystallization. The angle 

 of extinction given, is that obtained by measuring against the axis ot 

 elongation of the tibers. which is doubtless the verticaU-iystallogiapliic 

 axis. 



The size and shape of the rtbers in both asbestos proper and antho- 

 phyllite is found to be quite variable, but I can not discover that there 

 is any constant dittereuce. The Sails IMountain material (No. Gl.>.")7, 

 U. S. N. M.) occurs in the form of a massive aggregate of bundles of 

 short radiating tibers, rarely 20 mm. in length. The mineral is sott, of 

 a somewhat brittle nature, but in small tibers very Uexible, though 

 scarcely elastic. Under the microscope the interference colors are 

 very faint, scarcely discernible in the smaller fibers: extinction is 

 always parallel with the axis of elongation. The composition is that 

 of a hydrated anthophyllite. 



The Nacoochee (White County) material (No. 00842. U. S. N. M.) is of 

 a beautiful snow-white color in the mass, but colorless in single tibers. 

 The fibers are long, smooth, of very uniform diameter throughout, flex- 

 ible, but breaking with rectangular cross fractures. The libers not 

 infreipiently show a cross parting at right angles to the axis of elonga 

 tion. The mineral is not at all pleochroic, and the tibers always extin 

 guish parallel with the axis of elongation. The outline of the fiber is 

 polygonal. Other materials from Cleveland, in this same county, are 

 precisely similar, both in physical and chemical properties. The Kabnn 

 County (Georgia) material (No. 50351, LT. S. N. .M.) is colored brownish 

 by oxidation, and, on casual inspection, is coarse-fibered. The fibers 

 are long, somewhat stiff, but flexible, though not elastic. The ultimate 

 product of hbration, obtained by rolling the material between the 

 thumb and fingers, has a somewhat splintery look under the micro- 

 scope, the thin fibers, some 0.002 mm. in diameter, running out to a 

 point at the end. Extinction parallel with axis of elongation. 



