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

= + O.50253 i + 0.80422 £. + O.3173O k n

b = 64.5 h

b = 18.5 —D = - 0.85594 i + 0.40826 j_ + 0.31730 k •D X —D 0 o = + O.12564 i - 0.43104 i + 0.89352 k The bisectrixes of the optical vibration directions of the twin members A and C result in the twinning axis of the Carlsbad law. = + 0.47813 i + 0.37647 A + 0.79351 k = + 0.47627 i + 0.38401 J_ + 0.79102 k The two [npj are very close to each other, thus the value of ZT, cannot be taken into consideration. The mean value of bi—Ib sectrixes of the^nj andPn^J optical symmetry axes are computed by vectorial addition and this value will be considered as the [pOlJ zone axis. Z

T = + 0.47720 1 + 0.38024 i + 0.79227 k When the third bisectrix was disregarded the fact should be investigated that whether the acute bisectrix of the two^n^J lies to 90° from the value obtained above (Zj) or not. As a result of this the above-mentioned value hardly deviates from the right angle, it is 89.99°. On the basis of the scalar multiplication M-j. and Zj lie 90.26° from each other. Kj is computed by vectorial multiplication. Z

T X M 0 o = - 0.21281 i - 0.82469 j. + 0.52398 k The twinning axis between the members C and D is computed in the same way. The bisectrixes which approximately coincide are marked by the letter 1_.