We have designed and grown a new single crystal FeNi(SO4)(2) (.) 12H(2)O (FNSH) used as optical bandpass filters. The deep green block crystal with a dimension of 25 x 25 x 32 mm(3) has been grown by cooling solution method. Its parameters of crystal structure, transmission spectrometry in the range from UV to near IR wavelengths, and thermal properties are reported. (C) 2002 Published by Elsevier Science B.V.