408 



PROCEEDINGS OF THE ACADEMY OF 



[1895. 



PRELIMINARY NOTE ON A NEW ALKALI MINERAL. 

 BY WARREN M. FOOTE. 



While searching recently at Borax Lake, California, for the rare 

 species Sulphohalite, Mr. C. H. Northup discovered what he con- 

 sidered to be a new form of that mineral. 



The crystals were found during a laborious working of the tailings 

 which came from an exploratory boring known as the "New Well," 

 made by the Borax Lake Mining Company, and were formed in a 

 clay which was reached at a depth of about 450 feet. They were 

 at once forwarded to Dr. A. E. Foote, to whom the writer is indebted 

 for the material used in this examination. 



Crystallization, etc. — The mineral crystallizes in bright and 

 perfect octahedrons of a diameter rarely exceeding one centimeter. 

 Fractured crystals show in the interior a cross formed of faint lines 

 running perpendicular to the octahedral faces. Dark planes (which 

 were sharply defined in the interior of every specimen examined), lie 

 parallel to cubic symmetry thus passing through the angles of the 

 octahedron and dividing it into eight parts, each part containing a 

 distinct group of striae. 



The same thing is noticeable in the clearest of the complete 

 crystals, a bundle of lines coming from the central nucleus to the 



centre of each face. The accompanying sketch will give an idea of 

 the interior structure as appearing in a broken crystal. 



This remarkable phenomenon is strikingly similar to that observed 

 in Boleite cubes (figured by Bombicci in a memoir on Mimetical 



