238 HAROLD L. ALLING 
It will be seen that in order to limit the feldspar species to 
definite areas in a three-component ternary diagram the potash- 
lime series must be classified, in analogous fashion, to that already 
proposed for the soda-lime and potash-soda binaries. For feld- 
spars of the K-Ca series, analogous to soda orthoclase and potash 
albite, the terms “lime orthoclase” and “‘potash anorthite,’’ respec- 
tively, are suggested as meeting the present requirements. 
THE BARIUM-POTASH FELDSPARS—-HYALOPHANE SERIES 
The name hyalophane is said to have been proposed by Walters- 
hausen in 1855: from the Greek, tados, “glass,” and gavecba, 
“to appear,” alluding to its transparency. It is described as a 
barium-bearing feldspar found in transparent crystals similar to 
adularia. It is exceedingly rare in nature, the most famous 
locality being in the white dolomite of Binnenthal, where it was 
formed as the result of igneous contact action. 
The melting-point of celsian is not known, and furthermore very 
few suggestions have been found in the literature that would 
indicate the probable nature of the thermo-equilibrium diagram. 
Iddings gives: m(KAISi,Os), 1(BaAlSi,Os), suggesting isomor- 
phism similar to that possessed by the plagioclase series. Winchell 
gives a plot of the indices of refraction which incline toward higher 
values with increasing barium content, which is strictly analogous 
to the plagioclase system. Iddings supplies data for the construc- 
tion of the specific-gravity curve, which takes the form of a straight 
line. Clarke? quotes the opinion of Standmark: that “the mineral 
celsian . . . . is monoclinic and isomorphous with orthoclase.” 
Klockmann‘ likewise expresses the same view. In speaking of. 
hyalophane ina more restricted sense, Clarke says: ‘‘Hyalophane 
and other barium feldspars are mixtures of orthoclase and celsian.”’ 
In consistence with this view both Winchell and Iddings employ 
symbols and ratios which show a continuous range from Or to Cn, 
as follows: Or,, Cn;, Or,.Cn,, Or,Cn,, Or,Cn,, Or,Cn,,and Cn Figaae 
1W.S. Waltershausen, Pogg. Ann., XCIV, 134. 
2F. W. Clarke, U.S. Geol. Surv. Bull. 588 (1914), p. 35. 
3 Standmark, Zeitschr. fiir Kryst. und Min., Vol. XL (1907), p. 89. 
4 Klockmann, ‘‘Isomorphe mischung von K,Al1,SisOx6 mit BaAl,Si,Os,” Lehrbuch 
der Mineralogie (1912). 
