300 DESCRIPTION OF SOME CRYSTALS 



Description of some Crystals of Sulphate of Stron- 

 tian,from Lake Erie. By Dr. G. Tkoost. Read 

 August 6th, 1822, 



The south-western part of Moss island, in Lake 

 Erie, has furnished the miueralogical cabinets of our 

 country with some ornamental specimens of sulphate 

 of strontian, equal, if not superior in beauty, to any 

 collected at former known localities. It was not un- 

 til some time after its first discovery, that any well 

 determined forms of this mineral came under my ob- 

 servation, so as to enable me to determine to what 

 variety it belonged ; lately the zealous mineralogist 

 Mr. Jessup, furnished me with two crystals from his 

 collection, having most of their faces and angles pre- 

 served sufficiently perfect to enable me to submit 

 them to measurement. 



The description given by Cleaveland, in the se- 

 cond edition of his valuable treatise on mineralogy, 

 is rather vague, being applicable as well to the 

 varieties of sulphate of barytes, as to those of the sul- 

 phate of strontian, the same forms existing in both 

 minerals, and as is justly remarked by the Abbe 

 Haiiy in his Tableau de Mineralogie, " crystalliza- 

 tion has co-operated to approximate two substances, 

 already so nearly related by their other properties, 

 by assigning to them forms, which seem to have been 

 cast in the same moulds ; the goniometer alone, is 

 here the compass which can guide the observer." I 



