Composition of some Norwegian Minerals. 67 



II. — Tyrite. 



The other mineral which in external appearances might be 

 confounded with Euxenite, was found on the same island by- 

 Mr Dahl, at a place called Hampemyr, and was crystallized 

 in prisms, having a quadratic section, but too irregular and 

 unreflecting to admit of measurement, and one apparently 

 belonging to the tetragonal system. Fracture conchoidal ; and 

 no trace of cleavage apparent; exceedingly brittle; hardness 

 6*5. The specific gravity of a crystal was 5-30, and of a 

 massive piece was 5*56 at 60° Fahrenheit. It scolour and 

 lustre were perfectly the same as those of Euxenite, and it is 

 translucent in thin splinters. 



When heated in a glass tube it decrepitates strongly, evolves 

 water, and the powder resulting from its decrepitation is of a 

 brilliant yellow colour. 



Before the blow-pipe it is soluble in borax to a glass of a 

 reddish yellow colour when warm, but colourless on cooling. 

 In phosphate of soda and ammonia it is soluble with difficulty, 

 and appears to leave portions undissolved. The glass is 

 greenish yellow whilst hot, and green when cold. 



The analysis was conducted as follows : — 



A portion, in fine powder, weighing 29-42 grains, was 

 cautiously heated to redness, when it became of a greyish 

 yellow colour, and the loss was estimated as water. 



Another portion of mineral finely pulverized was digested 

 with pure concentrated sulphuric acid in a platinum vessel for 

 a considerable time ; it appeared to decompose easily and 

 completely, leaving a white powder, which was several times 

 successively digested with sulphuric acid well worked with 

 water, and weighed. 



This substance reacted as columbic acid, was of a pure white 

 colour when cold, but became intensely yellow when heated, 

 recovering, however, its original colour completely on cooling. 

 It was readily soluble in hydrofluoric acid, and this solution 

 deposited stellar groups of crystals on concentration. 



The solution was then precipitated by ammonia, filtered, and 

 lime determined in the filtrate by means of oxalate of 

 ammonia ; no magnesia was found to be present. 



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