Partially ordered domain structure is discovered for the first time in strontium tetraborate single crystal that is not known to be a ferroelectric. Domains are visualized by etching and are shown to have the form of sheets with domain wails perpendicular to a-axis. The structure is rather well-ordered along b and c crystallographic axes of the crystal but highly randomized along a-axis. (C) 2007 Elsevier B.V. All rights reserved.