O złożu nefrytu z Jordanowa (Dolny Śląsk)

Abstract

NEPHRITE DEPOSIT FROM JORDANÓW (LOWER SILESIA) Summary The paper presents some data concerning the geological setting, resources, history and exploitation and use of Lower Silesian nephrite deposit as well as physical properties of the nephrite. The nephrite deposit occurs in serpentinites in the form of pockets and veins variable in thickness and highly irregular in course. The nephrite accumulations are primarily related to the zones of serpentinite displaying traces of heavy dynamic and substantional alterations. The deposit occurs on southern slopes of Nasławickie Wzgórza, about 2 km WNW of Jordanów. It is exploited in a quarry about 3000 m2 in size. The nephrite resources are difficult to estimate accurately but they seem to be rather small. However, it is highly probable that other nephrite deposits occur in this area. At present the author is preparing a detail programme of nephrite prospecting in the Jordanów area. Jordanów nephrite is the product of alteration of serpentinites under the influence of injection of post-gabbro magma rich in water vapor, which was the main minerallizing agent. The nephrite is related to the occurrence of minerals such as diopside, zoisite, grossular, chrome hydrogrossular, vesuvianite, clinozoisite, prehnite, pumpellyite, desmine, tremolie, actilnolite, clinochlore, etc. The nephrite deposit was found by H. Traube in 1885. Jordanów nephrite macroscopically is characterized by darkgreen colour and by various sades of green when polished. Its hardness equals 6 in Mohs scale. Increase in exploitation of Jordenów nephrite would be very advantageous from the point of view of economy as the nephrite is one of the most beautiful in the world. The products of the nephrite sell well and the present production of jeweller's work of the State Enterprise "Skała" at Jordanów is relatively small, insufficient even for the internal market.