GEM CORUNDUMS AND ZIRCONS FROM THE PRIMORYE PLACERS

摘要

Description is done for sapphires, hyacinths and chromspinel, magnetite, enstatite associated with them in heavy concentrates and related to alkaline basalts. Transparent blue, blue-green, green, sometimes polychrom sapphires are represented by rolled crystals from 2-5 to 30 mm in size. Occasionally, silky and star-shaped stones may be found also. Chemical analysis data and optical absorption spectra show that coloring is connected with Fe and Ti ions. In-gly rolled crystals from 1-3 to 25 mm in size. They are transparent orange, orange-yellow or brown-red. While heating hyacinths loss their colour and become completely colorless. Zircons correspond, by their chemical composition, to a rare variety-naegite: with 4.59-6.14 percent Ta_2O_5, 3.22-3.59 percent Nb_2O_5 and 3.98-4.09 percent ThO_2. In general, obtained results support the notion that all the above mentioned gem minerals are related to the alkali basalts formation.