105 



form. The gyrolite is partly protruding in tiie innermost cavity 

 as small crystal tables without determinable faces. The cleavage 

 folia of the gyrolite are rather even and etching figures can 

 be formed upon them of a quite rounded shape; the substance 

 is rather impure and the specific gravity is 2"383. 



6. Ivnarsuit (Skarvefjeld) and Karartut on the south 

 side of Disco, district of Godhavn. Here have at very difi"erent 

 times, been collected some specimens of the mineral, which 

 show so much resemblance to each other that they must be 

 considered as having come from the same place, the two loca- 

 lities being, in fact, very close together. The gyrolite is found 

 in cavities in dolerite, the diameter of the cavities is up to 

 1 dm. The first formed mineral is natrolite, formed as very 

 regular radiating masses from which fine needles protrude 

 through the other minerals. Upon the natrolite the gyrolite 

 is formed, covering directly the walls of the cavities where 

 the natrolite is wanting. Innermost there are large (2 — 3 cm) 

 crystals of apophyllite implanted on the two first formed mi- 

 nerals. The gyrolite has the form of fine spherical masses 

 (c. 1 cm in diameter) sometimes traversed by natrolite needles 

 but mostly very pure; crystalline faces are found on the out- 

 side but they are too small to be determined. The cleavage 

 folia are somewhat curved and it is not possible to produce 

 regular percussion figures upon^them; etching figures of a quite 

 circular form can be produced with hydrofluoric acid. The 

 specific gravity, which, owing to the purity of the mineral, can 

 be determined very exactly, is 2*418. Optically this gyrolite 

 is sometimes feebly biaxial, the axial angle, 2E, going up 

 to с 10°. 



7. Kar usuit in Disco- Fjord, district of Godhavn. The 

 gyrolite from here, collected by Rink, is one of the finest and 

 best developed examples of the mineral. The first formed mi- 

 neral is in some places radiating fibrous masses, perhaps me- 

 solite, in other places a rather hard, white, quite homogeneous, 



