Structural Features and Composition of Amber from Placers on the East Coast of Sakhalin Island

Information on fossilized resin—a valuable raw material for chemistry, agriculture, and medicine—from the Russian Far East is scarce and insufficient. We studied an extensive collection of samples of amber from beach placers from the mouth of the Najba River to the village of Starodubskoe (South Sakhalin). The sources of amber deposits were erosional local coal deposits from the Paleogene age. The shapes of the wreckage were mostly wrong, squished, flow-like, round and drop-like. The transparency of the samples ranged from perfect to opaque. The textures were solid and flow-sandwich. The color ranged from light yellow to brownish or cherry red. Amber contains numerous microscopic minerals, organic materials, and gaseous inclusions. Based on spectroscopic infrared studies, most amber samples were found to be rumanites, while the rest are an intermediate type between rumanites and retinites. The central part of the sample may have a composition of the rumanite and peripheral-zone retinite. Two main compositional features of these natural resins are the ratio of aromatic to oxygenated hydrocarbons, and the ratio between the ester and the carboxyl groups in the oxygenated compounds. The amber coloration is mainly determined by the distribution of bitumen admixture originating from bitumen crusts of the amber pieces, which also determines the color zoning of the specimens.