30 Dana and Wells — Nexo mineral, Beryllonite. 



crowded together on an irregular wavy surface passing through, 

 a crystal after the manner so common in smoky quartz, or 

 again more or less regularly orientated, parallel to the vertical 

 axis or inclined to it in lines of 45° or 30°. The last be- 

 comes a Y-shaped arrangement of the minute inclusions in 

 some restricted areas, as is shown in figure 10. Figure 13 

 shows the usual arrangement and common forms of the cavities 

 (X90). As a rule these cavities, even the smallest, contain 

 each its own bubble, and very frequently two bubbles are noted 

 (cf. fig. 11) often of nearly the same size. This fact, the disap- 

 pearance of the second bubble with slight rise in temperature, 

 and further the presence or absence of a broad dark rim to the 

 bubble show the nature of the liquids and gases present. In 

 many of the cases we have water with liquid carbon dioxide, 

 and frequently also within this carbon dioxide gas. Occasion- 

 ally the bubble appears to be air in water, and more rarely the 

 cavity is partially filled with a liquid (C0 2 ) which does not wet 

 its sides. Solid inclusions, sometimes macroscopic, are also 

 noted. 



Chemical examination. — Qualitative tests showed that the 

 mineral is slowly but completely soluble in acids ; that it is an 

 anhydrous phosphate of sodium and beryllium containing no 

 other acids and bases, and especially careful tests proved the 

 absence of fluorine, aluminum, potassium and lithium. ' Before 

 the blowpipe it decrepitates and fuses about 3 to a somewhat 

 clouded glass, coloring the flame deep yellow with a tinge of 

 green on the lower edge. 



A quantitative analysis gave the following results : 



Calculated for 

 IV. V. VI. Mean. Ratio. NaBeP0 4 . 



55-8fi-4-142-=-392=l- 55'82 



19-81 19-84-r-25-2 = -787 = 2- 19-81 



23-68 23-59 23-64-4-62- =-381=1- 24-37 



0-08 



I. II. 



in. 



P 2 6 , 56-09 55-66 



55-84 



BeO, 19-87 



19-85 



Na 2 0, 



Tgn., 0-07 



0-09 



99-42 100-00 



It is evident from this analysis that the mineral has the com- 

 position represented by the formula Na 2 . 2BeO . P 2 6 or 

 JSTaBePO,. 



Method of analysis. — In I the P 2 B was determined by the 

 molybdic method in a sample of about 0*5 gr. The other five 

 samples were of about 1 gram each. In II, III and TV the 

 substance was fused with $Ta 2 C0 3 and, after treating the mass 

 with water, the BeO was filtered off and weighed, while in II 

 and III the P 2 6 in the filtrates was determined by the usual 

 method.* A trace of P 2 6 amounting to 0*17 per cent re- 



* This method for separating BeO and P 2 6 was used by Penfield and Harper 

 in their analysis of herderite : this Journal III, vol. xsxii, p. 107. 



