Copper Acetate(WSDTY) calcium acetate hexahydrate, a compound with formula CuCa(CH3COO)4·6H2O. It is an example of double salts (wiki): salts, having two different anions or cations. For comparison, crystals of pure calcium and copper acetates are put at the sides. Left crystal is calcium acetate (wiki): Ca(CH3COO 2·H2O. The crystals are colorless, their form resembles needles. The specimens on the photo were made accidentally a year or so ago. I've forgot a flask, containing mix of calcium acetate and acetic acid on the shelf. When I opened it, these transparent needles were on the bottom. This crystal have triclinic crystal system.

Seemingly black (actually dark blue-green) crystals on the right are copper acetate monohydrate: Cu(CH3COO)2·H2O (wiki). I've grew them half year ago, slowly evaporating saturated solution of copper acetate. This crystal have monoclinic crystal system. And finally, in the middle is the new addition to my collection: double salt, copper-calcium acetate hexahydrate, CuCa(CH3COO)4·6H2O. It has prismatic form, with improper 8-gon at the base. This reflects its structure, which is different from the both pure acetates; it is tetragonal.

Alas, the photo can't reproduce the beautiful blue color of this crystal. It is blue with a light violet tint, different from the well known copper sulphate. The crystal was grown rather fast, by the method of cooling supersaturated solution. Because of the fast growth, it is not completely transparent, and bases of the prism have some visible defects. Nevertheless, it's beautiful.

Click Cuprous Chloride to learn about more information