Growth and etching of calcite crystals

Single crystals of calcite (CaCO₃) have been grown by the method employed by GRUZENSKY , using an aquoeus solution of CaCl₂ and a solid (NH₄)₂SO₃, The chemical reaction takes place according to the following equation: CaCl₂ + (NH₄)₂SO₃ CaCO₃ + 2 NH₄Cl The crystals grown by this method are about 0.2 to 0.8 mm in edge dimensions. Synthetic calcite crystals have been cleaved along (100) planes and the cleavage surfaces have been studied by multiple beam interferometry. The interferograms have revealed that the cleavages are quite flat. The cleavage faces have also been chemically etched and the etch patterns studied optically. By etching a cleavage successively for three different periods it was found that the bottoms of the point-bottomed pits follow a linear etch path. By etching a cleavage pair, one face in one etchant and the other face in a different etchant and by comparing the etch patterns produced, before and after polishing a cleavage face it has been shown that the etch pits nucleate at the sites of dislocations in the crystal. The etch patterns have also been compared with those produced on the cleavage faces of natural crystals. The density of dislocations in the syntheitc calctie crystals was generally less than the density of dislocations in the natural calcite crystals. The implications have been discussed.