THE MINERALOGRAPHY OF THE FELDSPARS 
261 
CHEMICAL AND MICROSCOPIC ANALYSES 
CaO K.0 Na.O MgO H.0O Total 
2.60 GSO 1 GoOB WS oao0'50 .90 | 100.00 
BoA, || Ds) || Os VUhallasnchoe IOI.37 
K-feldspar 
SiOz AO; 
Ti o.6 SOR ORE 63.53 | 24.05 
2 6 5.0 OC eR En 63.51 | 23.00 
Pep eyitesleie cokes 8 11.8 
2 oc og SO eae Tm 
Microscopic..... 10.0 
Na-feldspar 
74-5 13-7 
76.0 hat 6 9/ 
75.0 I5.0 
Classification: Oligoclase. 
Analysis fr. 
Asch, The Silicates in Chemistry and Commerce. 
which are duplicated. Asch 9, Des Cloizeaux, Bull. Soc. Min. 7 (1884), 225. 
Analyses 9 and 34, 
Asch 34, 
Rosales, Pogg. Ann. (1842), 55, 109. Analyzed by Dirvell. 
Analysis 2. 
lyzed by Hagen. 
Asch, ibid., Analysis 71, Hagen, Pogg. Ann. 44 (1838), 329. Ana- 
See Dana, System of Mineralogy. Extinctions on: 
ARENDAL 
CaO Percentage oor Oo 
2.50 0-2 IO-12.5 
2.60 O-1.5 Q-I2 
2.81 o-2 IO-12 
4.20 .5-1I 2-4 
3. “Oligoclase, Sunstone,” Tvedestrand, Norway. (Specimen 970.) 
Microscopic examination, thin section: Oligoclase with inclusions of hema- 
tite, which are in all probability due to exsolution.t 
Extinction angles, crushed fragments: 
Mallard* Schuster ft Andersent Dana§ Alling 
(OHO) 2 isa. 2°—5° 3°34" Bae 2°-4° 2.5" 
(oor) 1°-1°27" T°r0! ig 1°30' I.0 
* EK. Mallard, Bull. Soc. Min. France, IV (1880), 104. 
t Max Schuster, Tschernaks Min. und Petrog. Mitt., III (1880), 164. 
{ Olaf Andersen, Amer. Jour. Sci. (4), XXX (1915), 379-80. 
§ James D. Dana, System of Mineralogy, sixth ed., p. 336. 
Inferred composition from the writer’s measurements, ignoring the potash 
component: Ab;Anjo. 
Inferred composition, considering potash component: 
K-feldspar........ 7.0 
Na-feldspar....... 70.0 
@a-feldspar 2.244230 
™ Olaf Andersen, Amer. Jour. Sci. (4), XXX (1915), 379. 
