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

The transformation of co-ordinates is performed first to the first complex. X' = Kj Y' = - M-j. Z* = Z Transforming the optical vibration directions of the member C the following values are obtainable: aj, = - 0.25141 i' - 0.47806 j ' + 0.83734 k» ~°o b_A = - 0.87899 i' + 0.47864 A

9 + 0.00602 k» ci = + 0.40490 i» + 0.73680 A' + 0.54665 k» ~°o The deviation from the unit vector in the third decimal is caused by the fact that the axes of co-ordinates are not exactly perpendicular of one another. The axes X'j and Y'j include and angle of 90.11°, the X'j and Z*j ones 89.72° while those indicated as Y'j and Z*

Y include 89.67°. Transforming the wanted twinning axis: Z* = + 0.49821 i» - 0.86800 A* - 0.00292 k» —

o — — The Goldschmidt values: 0= 150.26°, p = 90.17° The 0 value interpolated to the given anortite content is 149.60°, P is of course 90.00 . Accordingly, in this case the twinning law according to (130) can be determined. The twin crystals from the Börzsöny Mountains mentioned above are of about 80 per cent anortite content. The <p and values of the first-type Euler angles satisfactorily agree with one another, the 0 values, however, proved to be smaller than the typical values.