MAGMATIC DIFFERENTIATION OF IGNEOUS ROCKS 3309 
respectively about 26 Qu:74 orthoclase (72 Or+28 Ab), about 
26 Qu:74 Albite (Ab with little An and about 12 Or) and about 
40 Or:60 Ab+an (or 42:58). If we leave the inconsiderable 
St0,,1625° 
Ab, ca.1100° An, 1550° 
Fic. 5.—The ternary system Ab: An:SiO, (horizontal projection) 
admixture of An out of consideration, we must suppose for Qu:Or: 
Ab a ternary eutectic, with about 26 Qu and about 42 Or:58 Ab, 
consequently about 26 Qu:31 Or:43 Ab (or Abia,). 
We calculate the composition of these eutectics (see Tscherm. 
Miit., Vol. XV [1906], p. 385) as shown in Table IV. 
TABLE IV 
APPROXIMATE CALCULATION OF EUTECTICS QUARTZ: ORTHOCLASE (MICROCLINE): 
ALBITE (WITH LITTLE AN) 
Eutectic Qu: Ortho- “Ternary Eutectic”’ Batestic - Albit 
Percentage of SE Gar pou Oriecase Mite (88 Fis es AOE OS 
ils eee 26.0 |26.0 |26.0 |26.0 |26.0 |26.0 |26.0 |26.0 |26.0 |28.0 |32.0 
(Oi? 5:56 ae $828 |S8.B S854 [Stew leew anise [Bien So 4 8.6 |) B77 | B.6 
IND oo alts ieee pene BOP Ze LOn 2a 77 A2eA a IAEA 2OKOM|BOLON|O4e ON |O3HON|OORSmI5Gea 
JANOS 9 Bae O.§ || £5 || 2 9.5 | ¥o8 | BO | ©2© || ©c§ | Bog | B.© || ©.© 
[0.35 74-7 |74-45174.05]75-55|75-3 |74-9 |74.15]76.45|76.2 |76.45|76.9 
ALO, ../13.85/14.0 |14.25/14.1 |14.25/14.55]15.05/14.35114.5 |14.4 |14.15 
IKO somes 9.0 | ©. || ©. || G25] Kea5] Fas S225) wes | ug | wig! mAs 
NOR ts seks 285] QBo2S) Qo |) S$sO© |) Aw | A597 | ABs WoO || oR || Wee || One 
CAO a Qu || © O29 |) HO |] Ose GO |] WB 1] Cott!) On8 || Wale || 132 
