1895.] NATURAL SCIENCES OF PHILADELPHIA. 409 



Pyrite, Bologna 1893). Again, triangular markings on the surface 

 and a frequent parallel grouping of the octahedrons suggest a form 

 of interpenetration twinning, where the twinning axis is cubic as in 

 diamond. 



Color, varying from milky, pale yellow and greenish gray to 

 brown. Cleavage, imperfect. Fracture, brittle and uneven. Lustre, 

 vitreous. Hardness, 3.5 to 4. 



Chemical Examination. — Easily fusible. In a closed tube decrepi- 

 tates violently and gives off water, finally fusing to a gray mass. 

 Fragments and powdered mineral are almost unchanged by long 

 standing in water and the powder soluble with difficulty on boiling. 

 Readily soluble with effervescence in cold dilute hydrochloric acid. 

 Qualitative tests made on clear crystals, showed the presence of 

 carbon dioxide, chlorine and sodium with slight traces of calcium 

 and potassium, making it essentially a chlorocarbonate of sodium, a 

 composition quite as remarkable as that of other species peculiar 

 to this locality. 



Though found sparingly, it is hoped that material can be obtained 

 for a further and more complete investigation than the writer is at 

 present able to give. 



The name Northupite is proposed for this new species, since it was 

 entirely due to Mr. Northup's indefatigable zeal in collecting, that 

 the mineral was brought to light. 



