274 HAROLD L. ALLING 
Inferred Composition Potash Phase Soda Phase 
Keteldsparses see. seer 72 IO 
Na-feldspar.......... 25 80 
Ca-teldspatenneeeeeee 3 IO 
QUANTITATIVE MICROSCOPIC ANALYSIS 
Phase Percentage K-feldspar Na-feldspar Ca-feldspar 
Soda microcline. . . Bit. & 72.0 25.0 3.0 
Oligoclase........ 48.5 10.0 80.0 10.0 
Sodasmicroclinesr|peaeee eee eee 360.0 13.0 2.0 
Oligoclase: (Sa.5.5| S32 eee 5.0 39.0 5-0 
pROtal ae eee eee es, Se 41.0 52.0 7.0 
CHEMICAL AND MICROSCOPIC ANALYSES 
Analysis. A. A. Robbins, Collection on exhibition in the New York State 
Museum, Albany, N.Y. 
SiO. Al.O3 MgO CaO Na.0O K.0 H.0 SO; Total 
68.60 19.82 14, .96 4.57 5.25 .30 tr 99.64 
} 
K-feldspar Na-feldspar Ca-feldspar 
Chemical..... 41.5 51.8 6.7 
Microscopic...| 41.0 52.0 7.0 
Classification: 
Popular: Microcline microperthite. 
Technical: Microcline eutectoperthite. 
” Lenni, Delaware County, Pennsylvania. 
17. “Orthoclase, var. Delawarite, 
(Specimen 9gT.) 
Microscopic examination, thin sections: It is evident that this specimen 
is what a few mineralogists call antiperthite.t That is, the host is a soda- 
rich feldspar, while the blebs or “inclusions” are high in potash. 
The nomenclature here adopted calls for hyperperthite. This type is 
rare in nature. 
Extinction angles, crushed fragments: 
Soda phiasetan 2 isa (OLO) teeta 14.0° 
(GOT) ner Aner ANG 
(Sie els teticee Bee 
(GOT) eaten wey TOMSe 
t Ernst Weinschenk and R. W. Clark, Petrographic Methods (1912), p. 326. 
