516 J, Hae VOGR 
question. As an example we refer to Figures 17 and 18 of a quartz- 
norite from Erteli, Norway, consisting of about 60 per cent labra- 
dorite, 35 per cent hypersthene (with a little secondary hornblende), 
and on the average 5 per cent quartz, but without oxidic iron ore 
and without biotite. Some parts of the thin section show only 
3, r, or 2 per cent of quartz, but locally, as in the part photographed, 
the quantity of quartz rises much higher, even to 20 per cent. 
The relative proportions of the three minerals of the last stage 
of crystallization cannot be accurately defined under the micro- 
scope. We get the impression, however, that the percentage of 
Fic. 17.—Photomicrograph between Fic. 18.—Drawing (27:1) 
crossed nicols (24:1). : 
Hyperitic-structured quartz-norite from Erteli, Norway. Labradorite, with 
twinning lamellae after the albite law (and quite subordinate after the pericline law). 
Hypersthene (dark shading) with a little secondary hornblende. A little orthoclase 
(dotted in diagram) at the periphery of one or two labradorite individuals. The 
drawing represents about seven-eighths of the photomicrograph. 
ferromagnesian silicates in the final product of the solidification is 
quite small. As an estimate we may rate about 55 per cent labra- 
dorite, 35 per cent quartz, and ro per cent pyroxene. 
Their mutual proportions, however, will to a great extent be 
dependent upon the composition of the plagioclase and the pyroxene. 
Originating from the values mentioned, we may imagine a 
_ norite or gabbro with 3.5 per cent quartz, where the quartz and 
