WOLFF: LEUCITE-TINGUAITE FROM BEEMERVILLE, N. J. 275 
areas in which three elements occur. The most abundant is orthoclase, 
identified by its index of refraction lower than balsam, cleavages, and 
biaxial character; the analysis shows it can contain little sodium. 
Nepheline comes next, identified by its higher index, and lastly there 
are some isotropic areas of very low index with irregular cracking which 
are probably analcite. 
A little biotite, calcite, fluorite, quartz, brilliantly polarizing can- 
crinite(?) and small areas of indeterminate zeolites are in insignificant 
amount. Grains of pyrite are scattered through the rock. 
Analysis. 
The analysis was made essentially according to the methods used by 
Hillebrand.t| While it shows the general chemical characters of allied 
tinguaites, yet a striking difference is shown in the predominance of 
ferrous over ferric iron, combined with the high and nearly equal amount 
of the alkalies. The ferrous iron determination was made in duplicate 
by the hydrofluoric acid method, using a doubly tubulated bell-jar and 
sand bath instead of the water bath of Cooke (Pebal-Doelter method, 
see Jannasch, “ Leitfaden der Gewichts-Analyse,” p. 269), and the two 
determinations differed by only 0.02 per cent. The only mineral in the 
rock containing iron (except pyrite, which is separated in the tabulation, 
and a little biotite, etc.) is the pyroxene, and this is almost all in the 
ground mass where it has the optical characters of aegirine or aegirine- 
augite. A glance at the molecular proportions will show that there is an 
excess of the alkalies over the (AlFe).03 of 21 molecules and as there is 
no sodalite present it seems necessary to suppose this excess in sodium 
present in the pyroxene, where it must be combined in some way with 
ferrous and not with ferric iron, as would be the case were it aegirine. 
To better illustrate the difficulty, if we use a// the ferric iron, with one 
sixth ferrous, and the proper soda for aegirine proper, distribute part 
of the remaining soda and the potash with the proper alumina and 
silica between nepheline and orthoclase, part of the ferrous iron with 
the lime and magnesia in the hedenbergite molecule, we will find with 
3 per cent in the rock of aegirine, 13 per cent hedenbergite and 6 per 
It 
cent of a compound Na,Fe(SiO;),. The investigations of Merian ? 
and Mann ® indicated that aegirine-augite contained sodium in some 
1 Bull. U.S. G. S., No. 176. 2.N.J. Min. B.B., III. 1884, p. 252. 
3N. J. Min. B. B., II. 1884, p. 172. 
