A mollusc shell, the xiphoid from cuttlefish was found to be a substrate fa
vouring the deposition of aragonite crystals from stable supersaturated sol
utions at pH 8.50 and 25 degrees C. The crystallization was studied at cons
tant solution composition, thus making it possible for a relatively large a
mount of the overgrowths to be formed and to be identified exclusively as a
ragonite crystals. The apparent order found from kinetics data was n = 4.1
+/- 0.4, thus suggesting a polynuclear mechanism. A surface energy of 24 +/
- 3 mJ m(-2) was calculated for the growing phase and a four-ion cluster fo
rming the critical nucleus, according to the classical nucleation theory. (
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