84 On the Klaprothine or Lazulite of North Carolina. 



P : P (over a front edge) =100 6 

 P : P (over a side edge) = 97 24£ 

 P : P (over a middle edge) =131 12 



x (vertical axis) =1-652 



x (lnacrodiagonal) =1 



x (brachydiagonal) =0-9741 



The measurements of Phillips give for the octahedral angles, 

 as deduced by Hausmann, 99 16' (over front edge), 96° 39' 

 (over side edge), and 136° 20' (over middle edge). The posi- 

 tion of the crystals, as adopted by Phillips, is here changed, 

 however, his middle edge being made a front polar edge, and 

 the reverse. 



Many of these North Carolina crystals appear to possess 

 another form in addition to those enumerated above. This is 

 the front polar or macrodome, occurring generally on two opposite 

 edges only, and thus presenting a mouoclinic character, but 

 lying sometimes on only one edge, and being consequently (if 

 the mineral be trimetric) a tetartohedral modification. It is a 

 mere line, dull like the other planes, and too narrow to admit of 

 satisfactory measurement. The crystals are sometimes implanted 

 in one another ; but I have not detected any definite twin-combi- 

 nations. The crystals extracted from my specimen, together 

 with those exposed on the surface of this, do not amount, how- 

 ever, to more than ten or twelve in number. The hardness 

 of these crystals is equal to 5 "75, or very nearly to 6 0. The 

 specific gravity (one determination only) I found to equal 3"108, 

 a value corresponding sufficiently with that obtained by Smith 

 and Brush (3*122). The cleavage I have not been able to deter- 

 mine in a satisfactory manner. The blowpipe reactions are as 

 follows : — 



In the closed tube the assay gives off water and loses its 

 colour, becoming yellowish or greyish white. 



Per se, it exfoliates and expands greatly in bulk, changes 

 colour, tinges the flame green, and crumbles away without 

 fusing. 



In borax it dissolves very easily, imparting to the glass a pale 

 ferruginous tinge. 



In salt of phosphorus it dissolves also very readily, and with 

 slight effervescence. 



In carbonate of soda it dissolves partially, but the dissolved 

 portion is in great part precipitated as the glass cools, forming a 

 white enamel. If the bead be dissolved in a little boiling water, 

 a drop of nitric acid added to decompose the excess of carbonate 

 of soda, and the clear supernatant liquid be then poured upon a 



