Gemmological Characteristic of Two New Malachite Imitations

Two kinds of imitation products of malachite from Dehong Ruili jewelry wholesale market were tested in this paper. We used the conventional gemmological tests, infrared spectroscopy, UV-Vis spectroscopy and X-ray powder diffraction spectrometer to analyze two new types of malachite imitation, including gemmological characteristics, texture feature, mineral components and spectroscopy characteristics, comparing with natural malachite and other early malachite imitations. The results showed that both of the two imitation materials are repressed carbonates.The inorganic composition of malachite imitation sample A is mainly composed of calcite, including partial dolomite and very small amount of barite, which presents granular structure with two colours and dull hue.The malachite imitation sample B is pure calcite and presents fine texture, three colours bands and bright hue.They can be distinguished from malachite by its irregular and variable stripes, characteristic colour combination, low refractive index, relative density and hardness. Compared with the early malachite imitation, the carbonate(calcite, dolomite) content increased, while the barite reduced in the two malachite imitations, therefore they were more similar to natural malachite in material composition, heat needle test and hydrochloric reaction.In addition, infrared absorption spectrum and UV-Visible absorption spectrum can be used as auxiliary basis for distinguish.