» 
discovered near Platte mountain, Colorado, about twee 
184 General Notes. | February, 
such method uncertain. Descloiseaux, in a recent paper, has 
shown that although albite is the most constant of all the felé 
spars, it is subject to great variations, both as to homogeneity 
and optical characters. 
‘Tschermak holds that the soda-lime feidspars are all mixtures 
of a soda feldspar with a lime feldspar, the proportions varying 
to form a continuous series from a pure soda feldspar (albite) £ 
a pure lime feldspar (anorthite). Probably the only pere 
pure albite ever found occurs at Kasbék, Caucasia, where, accord- 
ing to Baerwald,? is a feldspar in which is no trace of lime or 
potash, and whose angles and specific gravity are almost identi- 
cal with those calculated by Tschermak as belonging to a theo- 
retically pure albite. 
“ Traité élémentaire de Mineralogie,” the subject of pseudo-sy'® 
metry is treated substantially as follows: After referring & 
labors of mineralogists. by means of the polarizing microscope 
upon the internal structure of certain minerals, such as ana te 
boracite, some garnets, etc., generally regarded as isometric, | 
shown optically to belong to another system ; and after re 
marks t! 
by an interior 
. . . ma. s 
hile admitting that the interior structure of a crys mite 
er. 
_ MINerALOoGicat Nores.—A new locality for topaz evel . 
: jn de 
north of Pike’s Peak. The crystals occurred in a po wee 
topaz were crystals of Mitchie goathite. fluorite, et ig the 
largest microcline crystal found measured eighteen i? a 
1 Bull. Soc. Min. de France, vI, 89. 
*Zeitsch, f. Kryst., VIL 48, . 
