Sinhalite，a rare borate mineral，was found in the Huayuangou boron deposit，K uandian County,Liaoning Province. It is associated with suanite,yuanfuliite,anhydrite and some other minerals in the boron orebody·Mineralogical studies show that it is yellow in color，granular in shape and longor short columnar in crystal form，similar to that of olivine. Weak pleochrosim:Ng-pale yellow，Np-nearly colorless;-2v =54º，H=6-7，D=3.48. Chemially, it is relatively enriched in A1 and Fe2+ but deficient in Mg. Unit cell parameters;a=9.893 (6)，b=5.676 (4)，and c=4.335 (3)A，larger than unit cell parameters of sinhalite from Sri Lanka. Sinhalite in the Huayuangou boron deposit was formed under the condition of regional metamorphismamphibolite facies.