Wood fossils are used all over the world as excellent materials for souvenirs, jewelry and collectibles. In 2014, a new wood fossil was found near the village of Kiparisovo in primorsky Krai district of the Russian Far East. Found in the northwest of the gravel quarry, at the intersection of rhyolite volcanic rocks, volcanic ash tuff and basalt. Sample sizes range from a few centimeters to two meters in length. Local jewelers began to use these wood fossils as souvenirs, collectibles, and began to appear in local jewelry stores, attracting the attention of Chinese tourists and creating demand for these raw materials in the Chinese market.
The Analytical Center of the Institute of Far Eastern Geology of the Far Eastern Branch of the Russian Academy of Sciences (FEGI FEB RAS) studied more than 100 samples, including their mineral composition, structural characteristics, as well as gemological characteristics. The sample as a whole showed white, yellow, Dali rocky, chalcedony, band, banded chalcedony with brown growth ring bands, and some carbonization and black coalification occurred.
The refractive index at the polished site is between 1.40-1.54, and its variation is related to the mineral composition, including opal, chalcedony or quartz minerals. It has a weak blue or green fluorescence at short wavelengths, and most samples are inert at long waves. The sample has a microscopic cell structure. Cells are, rectangular, and sometimes approximately square. The cross-section shows extremely narrow, single rows of horizontal wood rays. The absence of catheters, unique wood rays and tube cell types with marginal pores, the characteristics of the intermediate layers, and vertical resin catheters indicate that these samples belong to coniferous plants.
X-ray diffraction analysis showed that various wood fossils consisted of opal, quartz, and scale quartz. Depending on the local geological conditions, we can imagine the conditions under which these wood fossils were formed. The escape of rhyolite magma and late mantle magma forms a thick layer of volcanic ash and basalt flows, which flow into the basin, causing temperatures to exceed 1000 degrees Celsius. Lava covers the submerged trees as well as the thick sedimentary silt at the bottom. When the basalt flows into the water, the lava surface immediately cools, forming a pillow-shaped lava. The occipital lava is filled with glassy clastic rock.
As a result, the submerged trees are distributed under the glassy clastic rock and pillow lava. Some trees are vertically shaped under the pressure of lava flows. Some trees are scorched in basalt clastic rock, while those aged in silt remain unchanged. During silicification, the burned parts of the trunk become black, while the unchanged parts become white, light yellow, and brown. The trees buried in the ground were strongly deformed, and the trunks were flattened, cracked, and even broken. When silicification occurs, quartz or opal accounts for the cells of the tree, and silt becomes the main source of the Si element. Low alkali saturated water (volcanic ash saturated water, SiO2 content up to 72%) promotes the occurrence of this process. The silicon-containing aqueous solution penetrates into the wood, under anaerobic conditions, represents a local geochemical barrier, and the precipitation of free silica replaces the plant cells. Depending on the concentration of silicon in plant cells, opal, chalcedony or quartz are deposited. The above description allows us to imagine a spectacular picture of how nature created this wonderful combination of plant and stone worlds.
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