284 PROF. T. G. BONNEY ON CRYSTA^LLINE SCHISTS AND THEIR 



ellipsoidal form. I must leave these prisms also unnamed. The 

 mineral sometimes presents a slight resemblance to andalusite, 

 but the analj'sis seems to make this identification impossible. 

 J^aumann * appears to have regarded it as couseranite, for he names 

 the Nufenen Pass as a locality for this mineral. But the iden- 

 tification appears to be doubted by Studer, who is quoted by 

 Dr. von Fritseh in the passage from which the preceding analysis 

 is taken. This, however, does not correspond well with those 

 given by Dana, but comes nearer to some of those quoted under 

 the head " Agalmatolite ; " neither does the mineral exactly re- 

 semble any one known to me, though it is not very unlike cou- 

 seranite, and has a slight general resemblance to dipyre. I 

 suspect its relations are with this group of minerals. The analysis 

 corresponds more nearly with some forms of scapolite. (c) A 

 mica-like mineral which occurs in rather tabular small masses, 

 usually not exceeding -05 inch in diameter, and perhaps '03 inch in 

 thickness, presenting more or less rounded outlines and a very 

 distinct basal cleavage, a silvery lustre and a slight tinge of green 

 in colour. Under the microscope it is evidently authigenous, having 

 developed after the formation of a schistose structure in the matrix, 

 Avhich can be traced through the crystal. Sometimes, however, it 

 is fairly clean. It is colourless, very like a mica, but perhaps 

 slightly more " waxy " in aspect. The polarization-tints are rather 

 bright ; it almost invariably exhibits polysynthethic twinning 

 parallel with the planes (basal) of cleavage, and extinction which, 

 if not simultaneous, is very nearly so (and parallel with the same). 

 Both macroscopically and microscopically it seems to differ slightly 

 from a mica. Mr. Teall, after looking at my specimens, suggested 

 that the mineral might belong to the chloritoid group, and the more 

 I examine them the more probable this suggestion appears to be. 



Larger grains of pyrite are also common. These evidently have 

 been crushed out, for they form rather elongated clusters or streaks. 

 At each end, " under their lee," the quartz, calcite, and mica of the 

 matrix occur in slightly larger grains. 



Specimens cut from the finer bands, intercalated, as already 

 described, with those of the " spotted " rock, consist of a matrix 

 generally resembling that of the latter rock; but the grains are 

 rather smaller, there is less quartz and mica, and the specimens 

 more nearly resemble those of an ordinar}' impure fine-grained 

 limestone. The characteristic minerals of the coarse bands are 

 wanting, but there are grains of pyrite, and vein-like seams occupied 

 by calcite, with a very little quartz, (?) dolomite, white mica, and 

 perhaps a colourless silicate. 



One of the specimens from Scopi contains numerous joints of a 

 Pentacrinite. The matrix of this differs slightly from that of the 

 other examples in being a little more calcareous, decidedly more 

 carbonaceous and more irregular in its structure. Fragments of 

 organisms are frequent, such as I can identify as being Crinoidal. 

 In these the tubuli, infiltrated with carbonaceous matter, are often 

 * Elemente der Mineralogie, s. v. Couseranite. 



