1821.] Dr. TraiU't Description of some Minerals. 147 



Article V. 



Description of some Minerals found on the newly discovered 

 Antarctic Land. By Thomas Stewart Traill, MD. FRSE. 

 MGS. &c. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, Liverpool, July 2, 1821. 



The return of some of our ships sent to procure seals on the 

 shores of the newly-discovered Antarctic land has furnished me 

 with the following mineral substances, which are chiefly inte- 

 resting as tending to throw some light on the geology of that 

 dreary and desolate region. 



1 . Trap Rock. — This, in some specimens, is an amygdaloidal 

 greenstone, containing distinct grains of hornblende. It greatly 

 resembles the rock in which the zeolites of the Ferroe Isles are 

 chiefly found. In one specimen, now before me, it seems pass- 

 ing into basalt; and, when traversed by veins of quartz and 

 chalcedony, it becomes extremely hard, resisting the edge of 

 the knife, shows a blackish colour, and a conchoidal fracture, 

 and is perfectly similar to the rock of Portrush, in Ireland, in 

 which the ammonites are found. This latter rock I examined 

 about two years ago, and found it to be a bed between two 

 layers of common greenstone, with which, in some places, it is 

 intimately blended. 



2. Apophyllite in fine Crystals. — These are low rectangular 

 prisms, with the solid angles truncated, or replaced by triangular 

 planes. Some of the largest crystals, in my specimen, measure 

 more than 3-10ths of an inch in length, and 2-10ths in breadth. 

 The specimen forms a group upon rhombs of calc-spar, and 

 bears so striking a resemblance to a specimen of apophyllite 

 from Ferroe, that the eye cannot detect the difference between 

 them. The apophyllite of New South Shetland exfoliates rea- 

 dily in the flame of a common candle, it breaks down into 

 flakes in nitric acid (though not quite so readily as a specimen 

 from Ferroe), and at length forms a jelly. The pearly lustre is 

 confined to the terminal planes of the crystals, while that of the 

 sides is vitreous. These characters are sufficient to distinguish 

 the apophyllite from a few crystals of stilbite, which I found 

 adhering to the mass. Though none of the matrix accompanies 

 my specimen, the trap is most probably the rock in which this 

 mineral occurs. 



3. Stelbite. — A few crystals of this substance are mixed with 

 the apophyllite, and also shoot among quartz crystals in drusy 

 cavities. 



4. Druses, chiefly containing Quartz Crystals, with a few 

 Crystals of Apophyllite and Zeolite occasionally intermixed. — 



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