284 ASBESTOS AND ASBESTIFOBM MINERALS— MEBEILL. vol. xvm. 



A sample marked as from Tallapoosa County (?), Alabama, was 

 received from Prof. Albert H. Chester, of Rutgers College, I^ew Jersey. 

 It resembles very closely that of Mitchell County, North Carolina, and 

 occurs in tibrous bundles ten or more inches in length. This is also 

 anthophyllite, as shown by its chemical and optical properties. Material 

 received from Warrenton, Warren County, the same State, is of i)ure 

 white color, excepting where stained externally by iron oxide. It is 

 reduced readily by the thumb and fingers to fine, soft and silky fibers, 

 which do not ditfer materially from others mentioned. 



The San Diego material occurs in the form of hard, compact bundles, 

 somewhat difiicult to reduce to a fibrous condition, but capable of 

 almost indefinite subdivision. Under the microscope the fibers, either 

 singly or in bundles, give parallel extinctions. The bundles, even 

 though containing thousands of indivddual fibers, conduct themselves 

 as crystal units, the entire bundle behaving optically as a single fiber. 

 The larger fibers, although clear and compact, without indication of 

 having in themselves a fibrous structure, yet manifest their capability 

 of further subdivision by steplike ends, as in Fig. 4, where the rise of 

 each step represents the diameter of a fiber which has been separated 

 from it. 



As above noted, I fail to find any certain means of discrimination 

 between the anthophyllite and asbestos fibers by their shape alone. 

 Ol)tically there is, of course, a well-defined distinction, the asbestos 

 fibers giving extinction angles from 0° to 20°, according to their orien- 

 tation. These fibers, like those of anthophyllite, are angular in outline, 

 often compressed, at times of a very uniform diameter throughout their 

 entire length, or again tapering very gradually to a triangular point, 

 as shown in Fig. 5, which is drawn from a fiber of asbestos (Xo. 02550, 

 U. S. jS". M.) found in the " soapstone" (juarries of Alberene, Virginia. 

 The asbestos from Chester, South Carolina (No. 73402, U. S. X. M.), is 

 of a gray color, short-fibered, and rather brittle. The individual fibers 

 often show the cross partings, but have frequently acute terminations 

 and a splintery appearance. The material in Analysis 20 (see accom- 

 panying table), marked as from Cow Flats, Kew South Wales, it will be 

 observed, differs radically from that of the '' asbest-forminge mineral" 

 from the same locality as given by Hintze (Analysis 20). Our material 

 is of a beautiful wbite, silky appearance, very finely fibered, aiul show- 

 ing under the microscope clear, colorless, straight fibers of very uni- 

 form size throughout, ranging from 0.008 down to 0.002 mm. or even 

 smaller, and giving extinction angles varying from 0° to 17°. The 

 Corsican material is very similar, as is also that of Pylesville, in Har- 

 ford County, Maryland (noted later), excepting that the last is a trifle 

 more brittle and of a grayish hue. 



That from Aston, Delaware County (obtained from the Boston Soci- 

 ety of Natural History, through the kindness of Prof. W. O. Crosby), 

 occurs in short, beautifully silky forms, sometimes almost feltlike, or 



