1S13.] Minerals from Greenland, 105 



make several observations of the same sort : at one time I broke 

 a mass, and laid one portion under the rays of the sun^ while 

 the other was placed in the shade: the former was deprived of 

 the red hue almost instantaneously, while the other retained it 

 for some lime. This induced riie to try the effect of excluding 

 the iiirht: I accordingly wrapt up a mass, which after a period of 

 three }ears retained its colour nearly as fresh as ever. Among 

 the dodecahtdral crystals of sodalite, I obtained some having 

 six of tie solid angles replaced by planes of four sides indicating 

 the cube. 



Sahlife, 



This mineral has lately been considered by Hally as a variety 

 of augite. In iim collection it occurred massive; also combined 

 with sodalite. It was by means of the acute discrimination of 

 the Count de Bournon that the sahlite was discovered among 

 these Greenland minerals; like sodalite, it occurs in lamellated 

 masses ; its colour is white and greenish white, with a brilliant 

 shining surfoce; it divides with facility into rectangular prisms, 

 terminated by a plane which measures with the opposite sides 

 106° 15' and 73^ 45'. Parallel to the diagonal of the terminal 

 faces, there are indications of natural joints by which the prisms 

 may be divided vertically : for these observations I am indebted 

 to Mons. de Bournon. This substance is sometimes so intimately 

 blended with sodalite, that it is nearly impossible to discriminate 

 them ; a circumstance which is common with some other mi- 

 nerals. 



Tourmaline. 



Scarcely any cabinet is destitute of specimens of the fine 

 crystals of tourmaline, which are found in Greenland : it is 

 therefore surprising that in a collection so extensive there should 

 have been only one or two masses, containing a few very minute 

 crystals of this substance. They are well defined, however, and 

 imbedded in large grained granite, composed of quartz, very 

 white felspar, and light coloured mica. The large tourmaline is 

 found in a mountainous district 80 miles inland from the settle- 

 ment of Newhernhut; but as there are upwards of 30 colonies 

 along the west coast of Greenland, it is possible that Mr. 

 Gieseke did not visit them all. 



Amphiholc. 



This mineral was rather abundant in the collection. I found 

 some masses two or three inches in diameter, and one fragment 

 presenting a rhomboidal prism of 124^60' and 55° 30', being tlie 

 primitive form. The most remarkable specimens were crystal- 

 lized in prisms of six sides, grouped and solitary, and imbedded 

 in a granite rock. I met whh nothing to indicate a termination 

 but from thei? dimensions, some of the prisms measuring four 



