The crystal structure of kolwezite, (Cu, Co)2(CO3)(OH)2, was refined by Rietveld method from synchrotron X-ray powder data to Rp = 4.56%, wRp = 6.51%. Kolwezite, P21/a, a = 12.201(1), b = 9.354(1), c = 3.1494(3) Å, β=98.922(7)°, is isostructural with rosasite. Because of the Jahn-Teller effect, the Me1 polyhedron hosting Cu2+ only is strongly distorted towards a (4+2) coordination, while the Me2 octahedron, with major Co, is neatly a more regular one. The Me2+ polyhedra are connected through edge-sharing, forming “ribbons” running along [0 0 1] direction. These ribbons are interconnected by corner sharing to form “corrugated” layers, interlinked by the carbonate groups, giving rise to an infinite framework structure, with notation M − M = M−T. The Rietveld study of synchrotron X-ray powder data of synthetic cobaltoan malachites shows a decrease in unit-cell volume, with an anisotropic contraction of unit-cell parameters, with increasing Co content. The major progressive shortening of apical bonds in Me2 octahedra, with consequent regularization of the Jahn-Teller distorted Cu octahedra, drives a progressive compaction of the malachite structure; it is the main factor accounting for volume contraction in cobaltoan malachites.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.