Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 22. (Budapest 1925)
Koch, S.: Újabb előfordulású wolframit-kristályok Felsőbányáról
dominates, Jc is also well developed, y appears, however, as a small streak only. The a faces are, contrary to the usual occurence, horizontally librous, the Jc faces somewhat bent and dark, while the b and y faces are excellently bright, nearly on every crystal. Rather common, and very interesting are twins in juxtaposition in the direction of a, shaped as the swallow's tail commonly met with gypsum (fig. 1). These twins of the first ordre are developed either on one or on both ends, and become 2 to 3 mm. broad by 18 mm. length. The second type of wolframite also associated with chalcopyrite is rarer but more full faced as the first one and built up by the following five forms: a {100}, b {010}, / (101}, {Oil}, co [111}. On these small crystals, plates stretched along the c axis, the dominating face is a, besides it the X faces are well developed. The dominating a faces are not striated, bright and rather bent, the not smooth X faces give bad reflexions, while the small b stripes, as well as the f and œ faces are excellently bright (fig. 2). They were not found alone but in druses formed by hypoparallel growth. One of the prettiest was 5 l /a cm. long, 1 cm. broad and 1. cm. thick; it belongs to the Mineralogical Department of our Museum. Concerning the paragenesis we see that the chalcopyrite and quartz are always older, while the rhombohedrons of the dolomite and brownsper are younger. The third type is represented by the two full faced crystals received from Dr. FÜLÖPP. Their dominating form is Jc, the small crystals are stretched in this direction, they are like a steep chisel sharpened on one side. One of the two crystals is built up by eight, the other by twelve forms. The eight forms are: a {100} c (001} f {011} co {ill} b (010; d {310} k {502} a (121} The prismatic shape is atteined by the Jc and b forms, while the chisel appearance derives form the well developed a and d faces. Interesting is the appearance of c in the form of a small, uneven, dull face. The dominating k faces are uneven, less bright in comparison with the excellently reflecting b faces. The a faces are densely striated vertically, the prism of d is even and bright. The other forms of this combination are also represented by fine bright faces. On the fig. 3 I endeavour to reproduct a true form of the crystal. The other crystal received from Mr. FÜLÖPP which is the richest in laces, is built up by the following twelve forms:
