Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 3. 1972. (Budapest, 1972)

partly "sanidine" structure (2V -=c 44) can be established. Plagioclase forms hypidiomorphic or idiomorphic laths which are altered in most cases, thus it is difficult to find crystals 30 n 40 45 SO 55 60 65 70 75 2

Vx Pig. 2. Frequency of orthoclase 2V^ values 2. ábra. Az ortoklász 2Y^. értékeinek gyakorisága suitable for optical measurements. However crystals with an altered core and a fresh rim are fairly common. Zoning of plagioclase occurs as a rule (Plate 2. Fig. 3.). Untwinned crystals are rarely met with, they are composed of fine twin lamellae in most cases. Average An % and 2V values are as follows: Székesfehérvár Quarry Csala Forest Sárhegy Average An % 29 30 25 28 2V 82 83 77 81 X 83