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

The arithmetical mean which hardly deviates from the unit vector : Z, = - 0.02154 i - 0.42268 j_ + 0.90600 k o The Roc Tourné twinning axis computed from Mj and Zj by vectorial multiplication: K, = + 0.62634 i + 0.70056 £ + 0.34172 k o The bisectrixes of the optical directions of the members C and E: T = + 0.13588 i + 0.89973 A + 0.41473 k o T

b = + 0.14772 i + 0.89511 1 + 0.42067 k o T = + 0.13274 i + 0.88881 £ + 0.43861 k c

o Mean value : T = + 0.13878 i + 0.89455 I + 0.42467 k —

o — •"- — The bisectrix of the (010) face normal of the two complexes: T

M = + 0.13578 i + 0.88768 j_ + 0.43998 k o The deviation is small, in the following the values obtained from the optical directions will be used. The transformed values of the optical vibration directions of the member E: a" = - 0.56181 i" - 0.29503 J" + 0.77429 k" _E

o b" = + 0.78552 i" - 0.48320 j" + 0.38896 k" ~

E

o c" = + 0.25757 i" + 0.82545 j" + 0.49823 k" The transformed values are valid for the following system of co-ordinates :