Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 4. 1973. (Budapest, 1973)

Transformed values of the optical vibration direction of the twin member C: a£ = - 0.46817 i" - 0.34860 j_" + 0.81209 k" bU = + 0.82967 i" - 0.49165 A" + 0.26461 k" °o ç" = + 0.30702 i" + 0.79746 A" + 0.51911 k" o Transformed value of the twinning axis: z" « - 0.49685 i" + 0.86780 A" + 0.00548 k" The Goldschmidt values: = 330.2° p= 89.69° Goldschmidt values interpolated to 65 per cent anortite: 0- 149.48°, p is of course 90°. This is the (Ï30) face, thus it corresponds to the twinning law according to (130). (Controlled by the first-type Euler angles.) Third twin crystal Mark of the sample: Szp.8.C. Place of sampling: "Szárazpatak" quarry in the western part of the Kövecses Mountain, east of Pilisszentlászló. The rock is a medium-grey - dark-grey porous andésite, its texture is porphyric-microlitic. Size of the porphyric components: 130 to 1.500 n. The plagioclases are zonal. The anortite content of the twin crystal shown in Pig. 4. is 85 per cent. Measurement data of the twin crystal shown in Pig. 4. are the following: I. = (010) cleavage and composition plane of the A and B complexes. n

x = 270° h

I = 55°