116 



mineral is not identical with any one of the species of mica 

 hitherto known, but that it must be regarded as a new member 

 of the mica group. 



The name of tain io lite that I have given the mineral is 

 derived from the Greek words racu'ca, a band or strip, and kiêoç, 

 a stone, because the crystals always have the form of bands 

 or strips. 



Tainiolite has been found only as crystals, and the 

 crystal individuals are , without exception , very small. The 

 largest individuals observed measure 6™"^ in length by 1°"" in 

 breadth, and the thickness is generally extremely slight, even 

 to such a degree that they bend when one blows on them. 



Like the other micas, tainiolite belongs to the mono- 

 clinic crystal system. As already stated, the crystals do 

 not allow of any accurate angular measurements. It is not, 

 therefore, w^orth while calculating axial ratios for the mineral 

 from the measurements obtained. Such ratios W'ould at all 

 events differ but slightly, if at all. from the axial ratios given 

 for the biotite on page 111, viz. 



а:Ъ:с = 0,57735 : 1 : 3,27432. ß = 90°. 



These axial ratios may then, for the present, be regarded 

 as applicable also to tainiolite. Referred to these axial ratios, 

 the forms observed on this mineral have the following symbols 

 (Fig. 9, Plate III): 



с = {OOI}, b = {010], e = {023}, 

 ё = {027}, fx = [Vw]. 



These forms have been determined from the following 

 angular values: 



Measured Calculated 

 (010) : (001) = 90° 90° 



(023) : (001) = G5°9' 65° 23' 



(023) : (010) = 24° 44' 24° 37' 



