Thermodynamic properties of copper silicate: dioptase: Cu6Si6O18·6H2O

The molar heat capacity of hydrous copper chloride: atacamite Cu2Cl(OH)3

“…In the temperature range (4 to 10.5) K we observed a small anomaly in the heat capacity of atacamite with a maximum at T = 8.6 K. A similar phenomenon was found for a synthetic sample at temperatures below 8 K by Kawaji et al (17) Recent studies (22) of the magnetic susceptibility of synthetic atacamite revealed the existence of a relaxation phenomenon below T = 8 K identical to that in spin glasses. We discovered anomalies in the heat capacities of other Cu-minerals such as azurite, (1) broshantite, (3) and dioptase. (4) We assumed these anomalies were connected with antiferromagnetic ordering of the magnetic moments of Cu 2 + ions as the temperature decreased.…”

“…This work was preceded by our experimental investigations of thermodynamic properties of copper minerals of oxidized ore deposits including malachite, (1) azurite, (1) chrysocolla, (3) broshantite, (4) and dioptase. (5) We chose natural minerals with compositions closest to the theoretical ones for the investigation.…”

“…Atacamite, Cu 2 Cl(OH) 3 , a hydrous copper chloride, is a typical mineral in oxidized mixed copper ores, for example in rich Udocan (Siberia, Russia) and Collauracy (Chile) deposits. These copper ores have a typical composition and consist of azurite, malachite, broshantite, and other copper minerals.…”

“…Thermodynamic modelling allows one to determine the optimum parameters of oxidized mineral sulfurization in technical hydrothermal conditions and to establish the quantitative equilibrium composition of solid, liquid, and gaseous components of the system. We have performed thermodynamic modelling of the equilibrium composition in the hydrothermal systems of (oxidized copper mineral + sulfur + water) for Udocan copper deposits (1,2) on the basis of new thermodynamic data obtained by us earlier.…”

“…(5) We chose natural minerals with compositions closest to the theoretical ones for the investigation. We prefer to use natural samples, because the synthetic analogues, often having different structural defects and additional surface energy contributions, are not always good models for natural minerals.…”