HYDROTHERMAL GROWTH AND DISSOLUTION BEHAVIOR OF CALCITE SINGLE-CRYSTAL IN NITRATE SOLUTIONS

Dissolution behavior of calcite in nitrate solutions was studied under hydrothermal conditions. Changes of pH value and FT-IR spectra of some hydrothermal solvents were examined after growth runs. The pH value of NH4NO3 solution coexisting with calcite crystals increased to around 7 from pH 4 in pure NH4NO3 hydrothermal solution without calcite. This behavior was closely related to the reaction of calcite with chemical species in the nitrate solvent. Some experiments were carried out to grow a calcite single crystal on seed crystals. In NH4NO3 solvent, the (1011) face is confirmed to be a more dominant face than the other faces. Thermal gradient and convection in a reaction vessel have to be strictly controlled to grow high perfect transparent single crystals. © 1990, Elsevier Science Publishers B.V.. All rights reserved.