Fig. 5

Crystals on the filter from the experiments with tap water at \({T} = 45\), 60, 80 and \(110\,^{\circ }\hbox {C}\). Pictures show aragonite crystals as dominating calcium carbonate polymorph: wheat-sheaf (\(45\,^{\circ }\hbox {C}\), \(60\,^{\circ }\hbox {C}\)), spherical (\(80\,^{\circ }\hbox {C}\)), and acicular aragonite (\(110\,^{\circ }\hbox {C}\))