286 ASBESTOS AND ASBESTIFORM MINERALS— MERRILL, vol. xviii. 



Thai of Piedmont be also finds all transition stages between comi^act 

 augite and asbestos. The first stages of the transformation are indi- 

 cated by a tissue of fine fibrous material on the terminal planes, whereby 

 the crystal form becomes obscured, the whole ultimately becoming con- 

 verted into a bundle of flexible fibers with a silky luster. Unfortu- 

 nately he gives no analyses to show how this '■ asbestus " differs, if at all, 

 from the original augite. E. Schumacher also describes^ the alteration 

 of dioi)side into asbestos in a manner quite analogous to that of augite 

 into uralite. The secondary asbestos thus sometimes forms parallel- 

 lying fibers a decimeter in length, or " verworren faserigen " masses. 

 The material occurs in a granular limestone. No analyses are given, 

 the determinations being based on optical properties; nor is there given 

 any suggestion as to the cause of the transformation. 



Before going further, the writer should state that the idea that the 

 fibrous structure might be but an extreme phase of uralitizatiou, pro- 

 duced by shearing, was adopted very early in the work of this investiga- 

 tion, and in perusing the literature and making his own observation, it 

 has always been with this in mind. Both literature and observation 

 support this idea to a limited extent, as will be noted as we proceed. 



In his work on the Mineralogy of Scotland, Professor Ileddle de- 

 scribes^ an "amianthus" of unusual if not unrivaled excellence as occur- 

 ring in the deep cut " goes" on the eastern coast of the Balta Sound, in 

 the Shetland Islands. The length of the fiber varies from 4 to 12 inches, 

 and the mineral is sufficiently soft to be readily rubbed down to an 

 unctuous pulp between the thumb and fingers. It occurs in thin rifts in 

 gabbro, and though not definitely so stated, the descriptions are such as 

 to lead one to infer that the libration may be but a phase of schistosity. 

 Indeed, he describes a highly fissile schistose mineral of essentially 

 the same chemical composition, which is convertible into a fibrous form 

 by beating, and which passes into the asbestos on exposure, or, as he 

 expresses it, the ''amianthus" seems to '-grow out of the solid and iissile 

 stone." This is almost precisely the relative condition of the fibrous 

 and compact anthophyllite at Alberton, Maryland, to be described 

 later. The composition of this "amianthus" is given in Analysis 34, 

 showing it to be a true asbestos. A second occurrence at Portsoy, 

 described by this same authority, is of interest as showing the mineral 

 in veins an inch iu width in a gabbro passing into serpentine, and with 

 fibers lying transversely to the veins, an unusual thing, he says, "as 

 regards asbestus." Although occurring iu serpentinous rocks, this 

 also is a true asbestos, as indicated by Analysis 36. The "hydrous 

 anthophyllite" first noted by Jameson, and afterwards by Professor 

 Heddle, as occurring at the Free Clinrch of Milltown, in Glen Trquhart, 

 Scotland, is described as an alteration product after asbestos. The 



'Zeit. der Deutscheu Geol. GeselL, XL, 1878, p. 494. 



"Miueralogical Magaziue, II, 1878; also Traus. Koyal Society of Edinburgh, 

 XXVIIl, 1877-78, p. 502. 



