232 On the Occw^rence of Natro-horo-calcite in Gypsum, 



The conditions under which this substance is found in loose 

 masses in the nitrate of soda beds, give it a peculiar interest in 

 a scientific point of view, and render it highly desirable that we 

 should have full details of all the circumstances of its occur- 

 rence. The district of Tarapaca has been as yet but little ex- 

 plored, but it would appear that it is chiefly volcanic, and it is 

 remarkable that up to the present moment boracic acid has never 

 been found abundantly except in volcanic districts." 



The rock in which I met with the mineral, in Marcb last, is 

 part of a very extensive formation of gypsum in the western 

 centre of Nova Scotia, and the precise locality a bed of it at AVind- 

 sor, on the Clifton estate, lately the property of Judge Halibur- 

 ton. My attention was first drawn to the other mineral I have 

 named at the head of this paper, the glauber-salt, as a curious 

 * stuff' which had attracted the notice of the quarrymen, and 

 which they called "salts." Upon the specimens of "salts" 

 shewn to me I at once saw that at least two distinct minerals 

 were present, and procuring sufficient of both from the spot my- 

 self, I submitted them to examination. I give the chemical 

 analysis in the first place, and afterwards the description of the 

 minerals and locality. 



The glauber-salt was easily separated in a pure condition, and 

 its analysis in the fresh state gave, 



Sulphate of soda, - - - - 44*54 



Water, 



55-46 



100-00 



showing that it was the ordinary mineral, 



NaOSO3+10HO. 



The second substance reminded me of the Tiza which I had 

 seen in the hands of Dr. Anderson, in Glasgow, an4 a careful 

 selection of pieces being made, it was proved by the following 

 results to be identical with that curious mineral. The water 

 w^as found by gentle ignition, the soda estimated as sulphate in 

 a portion of the dry residue from which the boracic acid was 

 expelled as fluorid of boron, the other ingredients in a separate 

 quantity, the boracic acid by deficiency. The w^hole results 

 were calculated upon the air-dry mineral, whicb was alwa^^s \ 



employed for analysis, and I obtained from the substance as it \ 



occurred : 



Soda, 

 Lime, 



8-36 

 13-95 



Boracic acid, - - - - - 41-97 



Water, * 34-39 



Sulpliuric acid, ... - 1*29 



Magnesia, ------ 0-04 



^ 



100-00 



