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

description is sketchy and even the author thinks re-examination to be necessary. Besides the above-mentioned dikes of basic character no others have been found. The material of the narrower dike (40 cm) of Sárhegy is completely weathered, while that of the thicker one (80 cm) is fresh at least at the central part. The rock of the Csala Forest dike is also fresh in the middle part and it is weathered in marginal parts. In the Székesfehérvár Quarry two weathered dikes 70-80 cm in diameter can be found. One of the two contains relatively fresh rock patches. Its mineral composition is quite different from that of the rock described by M. Vendl (1923). All the dikes of basic character, striking NE-SW can be traced for a few meters only. While the wall rock of dikes is granite on the Sárhegy and in the Csala Forest, it is aplitic microgranite at the Székesfehérvár Quarry. The dike rocks contain granitic inclusions especially in marginal parts. Aim of present study and investigation methods Our knowledge about the basic dikes of the Velence Hills has not been sufficient even to decide the question whether the dikes are really of lamprophyric character and if they are, the name kersantite is a proper one or not. In many respects 1ampropbyres seem to be "peculiar" rocks. They have a number of mineralogical, chami

cal and textural characteristics. It has been the author's principal aim to prove the existence or lack of these characteristics, and thus to be able to answer the questions above-mentioned. The optical properties of feldspar and hornblende crystals have been determined by means of a Leitz universal stage. At the measurement of axial angle the so-called direct method was used.