Petrified wood

Petrified wood

     (SiO₂)
     Among volcanic ores frequently there is a petrified wood, but it high-decorative versions are rather rare.
     Areas of distribution of a petrified wood are volcanic areas where there were eruptions of volcanos in the territories of distributions of forests of tertiary and other periods. These are areas of volcanic activity in platform and geological areas of Average Siberia where trunks and fragments of a petrified wood are marked in alluviums on the rivers Lenas, Vilyui, Vitim, Stony Tunguska etc., at coast of Kamchatka, in Georgia (Goderdzky pass). The deposits of a petrified wood in Kuznetsk area, on Ukraine, in Primorski Krai region, Armenia, Kazakhstan, Uzbekistan, Kirghizia and other areas are known.
     The specific structure of petrified wood in these regions is various: coniferous (a fur-tree, a pine) and deciduous (an alder, an ash, a birch, an oak etc.). The mineral wood rests underwent significant changes in connection with carbonization or petrifaction (replacement of organogenous or mineral substance). A.E.Fersman (Russian scientist) wrote about complex chemical process of formation of quartz, chalcedony, opal with preservation of the external form and ring structure of growth of a wood and even structure of cellulose (pseudomorphosis of replacements). It gives to a petrified wood the original beautiful shape and frequently non-uniform striped-spotty coloring from gray up to dark brown color. Silification of wood of siliceous solutions occurred as at high, and low temperatures in volcanic ore. Such processes as carbonisation, gypsuming, piritisation, iron plating etc., proceed at low temperatures in sedimentary ores. In the petrified wood deposited in ashes, meets noble opal (USA, state Nevada).
     Hardness of silificated petrified wood: 5,5 - 6 on Mohs scale.
     Break: like-shell.
     Shine: glass.
     On structure it silica (SiO₂) with insignificant quantity of impurity.
     The basic practical value have petrified fragments (especially chalcedony) of quartz structure, which can easerly process and an accepted smooth surface. The petrified wood is processed by diamond saws without oil which is absorbed and leaves dark stains. Polishing make on a pig-iron faceplate, and polish by oxide of chrome on a felt circle.
     The petrified wood is applied to manufacturing a beads, inserts in inexpensive jewelry, souvenirs. The polished plates or fragments of a petrified wood with bright ring figure are especially interesting to collectors.
     High-decorative qualities of petrified wood has in Goderdzskoe deposit in Georgia (pseudomorphosis of chalcedony and opal), Kurdumovskoe deposit in Primorski Krai region (opal), Chokoyanskoe deposit (chalcedony, coal substance, a carbonate of calcium), Lvovskoe deposit (quartz, chalcedony). The extracting of specified deposits are produced only in warm seasons by the opencast way.