Hexagonal tubular YAl3(BO3)(4) crystals of millimeter diameter were obtained by spontaneous crystallization from B2O3-SrO flux system. The sizes of these tubular crystals range from 0.5 mm to 6 mm in diameter, 0.2-0.4 mm in wall thickness, and 1-10 mm in length, which are obviously influenced by the cooling rate. A formation mechanism of tubular YAl3(BO3)(4) crystals was proposed, which inferred that lateral variation of solute supersaturation along (001) crystal face due to the fast growth speed along the [001] direction and the high viscosity of the solution led to the formation of tubular structures. (C) 2011 Elsevier B.V. All rights reserved.