264 HAROLD L. ALLING 
3. “Orthoclase, var. Adularia,” Eggerhorn, Switzerland. (Specimen 989.) 
Microscopic examination, thin section: Very coarse phantom twinning 
with wavy extinction. Some areas comparatively free from microclinic 
texture, and appear like perfect development of orthoclasic feldspar. 
Extinction angles, crushed fragments: 
Untwinnedh ye. ee (One) eee 7.2 
Untwinneds 2 ane ener (CoT)\s. oeciere ey 
Twannedl (yi. seers ee (Cro) eae 6.5 
CE WAR ede a ta i ween aise (Cor) hae 17 0 
Inferred composition: 
Keteldspat. -ote0ee 82.0 
Na-feldspar® jenn 16.0 
Ca-feldspars eevee 2.0 
The probable character of the feldspar is that it is in the process of invert- 
ing from soda orthoclase to soda microcline. 
Classification: Soda orthoclase—soda mitrocline. 
4. “Microcline,” Georgetown, Maine. (Specimen 995.) 
Microscopic examination, thin section: It is readily seen that the speci- 
men is a microclinic microperthite. 
Extinction angles, crushed fragments: 
Potash phase...55...-. (Cro) saa 6.0° 
(Glois) Stun TSS 
Soda phaseurnia eerie (CuO) ins be eee AvOw 
(Com enone ae ELOn 
Inferred Composition Potash Phase Soda Phase 
K-feldspar........... 88.0 I5.0 
Na-feldspar.......... 5.0) 750 
Ca-feldspatgaerrente 7.0 10.0 
QUANTITATIVE MICROSCOPIC ANALYSIS 
Phase Percentage K-feldspar Na-feldspar Ca-feldspar 
Soda microcline........... 83.5 88.0 | 5.0 7.0 
Oligoclasehwen neta wee 16.5 I5.0 75.0 10.0 
K-feldspar Na-feldspar Ca-feldspar 
Soda microcline........... WB 4.2 [Pe RHE ORS foo cicc.c 
Olizoclasé Asn eee eee Do & 12.3 1.6) oleate sree 
