Atacamite

Copper(II) oxychloride [1332-65-6], Cu2Cl(OH)2, is found in nature as the green hexagonal paratacamite [12186-OOA] or rhombic atacamite [1306-85-0]. It is usually precipitated by air oxidation of a concentrated sodium chloride solution of copper(I) chloride (13—15). Often the solution is circulated through a packed tower of copper metal, heated to 60—90°C, and aerated. 

The intermediate planes are alternately one-quarter and three-quarters occupied. This is the arrangement in atacamite, a modification of Cu2(OH)3C1 with the stacking sequence ... 

Atacamite (basic copper chloride) Bright to dark green... 

Asymmetric substrate, 13 664-665 Asymmetric synthesis, via chiral organoboranes, 13 664-671 ATI receptor, 5 158 Atacama Desert, sodium nitrate in, 22 844-845 Atacamite, 7 769... 

KEYWORDS Chile, copper, atacamite, anomalies. Pleistocene... 

Fig. 1. Distribution of copper deposits in northern Chile including those containing atacamite in the oxide zone. DFZ is the Domeyko Fault Zone and ACL is Antofagasta-Calama Lineament. The land between the High Andes and the coast is the hyper-arid central Atacama Desert.

Reich et al. (2008) measured CI in atacamite from Mantos Blancos, Spence and three other deposits. These show low CI-to-CI ratios (11xi0 to 28x10 ), comparable to previously reported ratios of deep formation waters. Further, CI-to-Cl ratios in atacamite correlate with U and Th concentrations in host rocks. This suggests that subsurface production of fissiogenic CI was in secular equilibrium with waters involved in atacamite formation. Because atacamite does not contain U or Th, production of CI is not continued once chlorine has entered the crystal structure from that time the CI-to-Cl ratio decreases with age. The fact that measurable Cl is present indicates that atacamite formation occurred less than 1.5 Ma ago (five times half-life of CI). 

Cameron, E.M., Leybourne, M.I., Palacios, C. 2007. Atacamite in the oxide zone of copper deposits in northern Chile Involvement of deep formation waters Mineralium Deposita, 42, 205-218. 

The Crystal Structure of Atacamit and the Crystal Chemistry of Cupric... 

P. Hartman, Epitaxial aspects of the atacamite twin, Cursillosy Conferencias, C.S.I.C. 

Fig. 3.9 SQWVsfor(a) azurite, (b) cuprite, (c) verdigris, and (d) atacamite, in contact with 0.50 M potassium phosphate buffer, pH 7.4. Potential scan initiated at +0.45 mV in the negative direction. Potential step increment 4 mV square wave amphtude 15 mV frequency 2 Hz [133]...

Fig. 3.11 Tafel plots for verdigris (A), atacamite (B), paratacamite (C), and cuprite (D) from linear scan voltammograms at sample-modified, paraffin-impregnated graphite electrodes immersed in 0.50 M potassium phosphate buffer (pH 7.0). Potential scan rate 50 mV/s...

According to the previous treatment, linear Tafel plots of n i/ip) on E were obtained for samples providing from different regions of the helmet. As can be seen in Fig. 3.15, 2D diagrams using Tafel slope SL) and Tafel ordinates at the origin 00) yield a distribution of samples in three groups one formed by cuprite (CI-11), one formed by atacamite (CI-4, CI-6, CI-9), and one formed by a mixture of cuprite plus atacamite (C-12). 

Frost RL, Martens W, Kloprogge JT, Williams PA (2002) Raman sepctroscopy of the basic copper chloride minerals atacamite and paratacamite implications for the study of copper, brass and bronze objects of archaeological significance. J Raman Spectrosc 33 801-806. 

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