We propose a new method of evaluating both interfacial energy a between melt and crystal and the activation energy of diffusion Ea by analyzing the crystallization experiment with the use of gas jet levitation method. We show that there arise three features of crystallization of a cooling melt sphere depending on sigma and E-a: (A) crystallization near the melting temperature, (B) crystallization from the hypercooled melt, and (C) no crystallization. Applying the present method to the experiment of crystallization of a melt sphere of forsterite composition, we evaluate its sigma and E-a to be sigma = 613 +/- 30 erg cm(-2) and E-a/k = (2.3 +/- 0.2) x 10(4) K, where k is the Boltzmann constant. (c) 2008 Elsevier B.V. All rights reserved.