A new type of PbHNSO 3 crystal has been grown by a gel method using agar-agar gel. TG-DTA and X-ray diffraction measurements have been performed on single crystal samples of PbHNSO 3 . It is found that the thermal decomposition of the compound starts at about 960 K. The space group (orthorhombic Pnma) and structural parameters are determined at room temperature with unit cell dimensions: a=8.4690(6), b=5.3934(4) and c=6.9530(4) Å. The crystal structure is found to consist of NSO 3 pseudo-tetrahedra, PbO 9 N 3 polyhedra, and NSO 3 -Pb-NSO 3 frameworks. The dark brown color of the crystal is suggested to be caused by the absorption of blue wavelengths of light which is due to the excitation of excess electrons in potential wells produced by the NSO 3 -Pb-NSO 3 framework.