256 ‘ HAROLD L. ALLING 
and Wright" have shown that the plagioclase from Limosa contains 
an appreciable amount of carnegieite in solid solution. 
The chemical analysis is as follows: 
SIO see amen ere en ete Sona) (CaO ie Sean) nee 10.66 
ALE Oya a Pecienaieres rey eterno 20.450 NaO: ict A eee 5-40 
Bez O a rrennia Uiyar. attest elo (65. » RaQ. Uh ea 74 
COWS tvs eee cae ec mnt xcs 17 | FLO: 2 s-ctis eee 36 
I [eed Oe aies ee BRS Baa By Onan ete ee .05 Total... tk cee 100.30 
They recast the analyses in terms of four components: 
Potash=component. ces... - KAIST Os rare eee 4.48 
Sodium component........-: IN@ATSIEOs reese eee 36.16 
Mimeicomponcnte seem aie CaAlSiO; eee sane 
CAGMEPIEIt eC. yah ines nai ae Nal ALSO; ee eee 5-58 
If, however, the presence of the carnegieite in the feldspar was 
not suspected and the analysis recast on the basis of only the 
three components then the result would be as follows: 
RotashicomipPoncnte ean ree 4.48 
Sodium componente rere ee 54.20 
Litas GOmANOOMGMNE, okodncsodoobenzscade 53-78 
with the excessive total of 112.46 per cent.. A short method of 
obtaining the proper composition of a carnegieite bearing feldspar 
can be secured by setting up the ratio, Na-component without 
carnegieite: 1 = Na-component with carnegieite: .6667. 
Because of the probability that many of the analyses here 
recast and plotted, even though tested by the method above men- 
tioned, are inferior to those now being made in many laboratories, 
there are limitations to the conclusions that can be safely drawn 
from their study and comparison. Yet it is believed that they 
illustrate beyond much doubt that the term “‘orthoclase” is used 
in a very loose manner, quite inconsistent with present-day stand- 
ards. Fair maximum and minimum limits for the range assumed 
by natural “‘orthoclase”’ specimens among the analyses examined 
were: 
K-feldspar Na-feldspar Ca-feldspar 
AONE S sitters 87.60 ies (OS E35 
CORE Saher: 49.20 48 .60 220 
« H. S. Washington and F. E. Wright, “A Feldspar from Limosa and the Existence 
of a Soda-Anorthite (Carnegieite),” Amer. Jour. Sci. (4), XXIX (1910), 52-70. 
