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

T£ = - 0.87105 i» + 0.49010 i* - 0.00095 k' When taking the opposed vector according to the inversion centre its Goldschmidt values will be:<£ = 119.35° and P • 89.95°. The interpolated theoretical value: 0= 119.41° and p= 90.00°. Consequently it corresponds to the (llO) face. Transforming the optical vibration directions of the member B: a' = - 0.25076 i» - 0.48172 j» + 0.83804 k* _B

o _ b' = - 0.88403 i» + 0.46739 1' + O.OO615 k' c' = + 0.39464 i» + O.74II5 y + 0.54556 k» _B

o _ Transformation is performed into the system of co-ordinates of the other complex: X" = K

IZ Y" = -M Z" = Z

1Z T£ = + 0.86826 1" - 0.49010 i" + 0.00736 k" 0= 119.35° P= 89.58° Seventh twin crystal This crystal occured in amphibole-andesite of porphyric-microlitic texture. Number of the rock sample: Nm 1/66. This sample derives from the abandoned quarry in the margin of the northeastern part of Nagymaros village, from andésite agglomerate. .The measurement data and vector components of the plagioclase grain shown in Pig. 8. are as follows: I. = the (OlO) cleavage and composition plane of the first complex containing the members A and B, n

x = 250° h.,. = 17°