Affiliation:
1. Russian State Geological Prospecting University (MGPI-RSGPU)
Abstract
Significant volumes of products from ammonites of jewelry and ornamental quality of the Ulyanovsk region are entering the Russian and world markets. Ammonites are associated with the Lower Cretaceous Hauterivian deposits and consist mainly of aragonite, calcite and pyrite. The walls and partitions of the ammonite shells retained the original aragonite composition. Also established inclusions of apatite, algodonite, pyrolusite, hematite, goethite, quartz, ferrihydrite, magnetite, uranium oxide, vernadite, todorokite, monazite, halloysite, plagioclase, kaolinite, glauconite, dolomite, graphite and organic matter. An important role in the formation of new mineral species was played by bacteria. Mineralization of undamaged ammonite chambers was carried out by the sequential formation of calcite and pyrite layers without metasomatic substitutions. The color of calcite layers is determined by the contents of Mn and Fe. Ammonites are characterized by high decorativeness and good technological characteristics; they can be mined in the coastal cliffs and the beach area of the river Volga without mining, without violating the environment.
Publisher
Central research institute of geological prospecting for base and precious metals
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