218 S. L. Penfield and G. S. Jamieson — Tychite. 



who first observed the new mineral and supplied the material 

 for investigation. A complete study of the chemical composi- 

 tion and physical properties of the new compound was subse- 

 quently made by Pratt, who found the composition to be 

 MgC0 3 . Na 2 C0 3 . NaCI, his results being published in this 

 Journal.* 



Being assured of the existence of a second, new, octahedral 

 mineral, associated with the northupite, Mr. Foote generously 

 responded to our request to send to New Haven his entire 

 stock of crystals in order that a search might be made for the 

 missing sulphate. The following simple method of testing was 

 employed, which did not in any way injure the specimens : 

 Some dilute nitric acid containing a little silver nitrate was 

 prepared, and with a broom-straw a minute drop of the liquid 

 was applied to each crystal. Thus, if chlorine was present, a 

 little silver chloride would be formed and the drop of liquid 

 would become milky-white. In testing several hundred crys- 

 tals in this way, only two were found which did not give the 

 reaction for chlorine. One of these was a small but perfect 

 octahedron, the other a small cluster of octahedrons, of some- 

 what inferior quality : together they weighed only about 0*10 

 gram. It was hoped, however, that by sacrificing the speci- 

 mens for chemical analysis sufficient determinations could be 

 obtained for deriving the formula ; but in this we were disap- 

 pointed, for, unfortunately, the analysis met with an accident 

 before a single determination had been made. We were thus 

 compelled to abandon the hope of determining the composition 

 of the new mineral until other crystals should be found in new 

 lots of the northupite. 



Recently our attention was called to the unknown sulphate 

 by observing in the stock of Mr. Lazard Cahn of New York 

 a supply of northupite crystals which he generously loaned to 

 us for examination, but when tested they all proved to be the 

 chlorine compound. Likewise Mr. Warren M. Foote of Phila- 

 delphia has been kind enough to send us his entire stock of 

 northupite, consisting of something over four thousand crystals, 

 among which we had the good fortune of finding one small 

 octahedron, weighing but 0*0109 gram. Curiously enough, 

 this was among the last ten crystals which were tested, and 

 was found after hope of obtaining the desired sulphate had 

 practically been given up. 



Artificial production. — Believing that the unknown sulphate 

 would prove to be closely related to northupite, and knowing 

 that de Schultenf had succeeded in making the latter arti- 

 ficially, it occurred to us that possibly the wished for sulphate 



* This Journal (4), ii, p. 133, 1896 ; also, iii, p. 75, 1897. 

 f Bull. Soc. Franc, de Min., vol. xix, p. 164, 1896. 



