82 



aegirine, elpidite, epididymite, parisite, elc. Like all the arfved- 

 sonite on Narsarsuk, it is evidently of secondary formation. In 

 general the crystals occur implanted on or between feldspar 

 crystals. The small aegerine individuals that form the kernels 

 of the arfvedsonite crystals have probably been previously im- 

 planted on the feldspar and afterwards been coated with arfved- 

 sonite substance. Small crystals of arfvedsonite also occur groAvn 

 together with large aegirine individuals in parallel position. 



16. Crocidolite. 



This mineral, whose character as an independent species 

 can as yet hardly be said to have been established beyond 

 doubt, has nowhere been met with as idiomorphic crystals. 

 Also on Narsarsuk, where it is by no means rare, it has 

 been found only as detached pieces of irregular form lying 

 among the gravel, or as secondary inclusions in other minerals. 

 The detached pieces always have a fibrous structure, which, 

 however, is often so fine as to give the mineral an almost 

 compact or earthy appearance ; in such cases it is only with 

 the aid of the microscope that the fibrous texture can be per- 

 ceived. In most cases, however, this texture is sufficiently 

 distinct to be observable by the naked eye. But rarely, and 

 then only in very small portions of the mineral, are the fibres 

 in parallel position. In general they are matted together into 

 perfectly felt-like masses. These masses are very tough and 

 can hardly be smashed to pieces with a hammer. The fibres 

 are soft and easily separated by the nail. In the apparently 

 compact masses there are sometimes small cavities lined with 

 an extremely fine felty mass of the thinnest fibres. Sometimes 

 the pieces of crocidolite have an oolitic structure, consisting of 

 concretions of the size of a hemp-seed. Externally these little 

 b.ills are somewhat angular and not very regular in form. Inter- 

 nally they consist of fibres radiating from the centre to the sur- 



