Peculiar nephrite from the East Saian Mts (Siberia)

During field investigations, a rare variety of nephrite was found in one of the nephriticbodies of the ultrabasite Ospino-Kitoj massif (the East Saian). The nephrite is homogeneous, lacking of anyspot-like structure typical of nephrite, and shows very good, although dim, grey-greenish translucency.Subtle internal features of the nephrite were observed under the microscope. Its structure is similar to textileweave made of two perpendicular sets of threads, arranged lengthwise (warp) and crosswise (weft). Thecompactly set and plastically deformed, micrometer-sized tremolite threads form the thicker warp thread(0.02–0.03 mm), while the thinner weft thread is composed of thickly placed, usually singular tremolitethreads. Comparing these features with the features of nephrites from the world’s deposits it is seen that thedifferences between them essentially consists in the internal structure. Peculiarity of nephrite from the EastSaian Mts lies in its structural, textural and mineral homogeneity, a rare trait of nephrite. It is worthmentioning that such a structure is not characteristic of the tremolite asbestos, which is also present as veinsin that deposit.