Specimens of a beautiful blue mineral recently found for the first time at Franklin Furnace have, within the past year, been widely circulated in mineral collections as cyprine. Specimens of this blue vesuvianite have been received at this laboratory, but when examined were found to be made up of such intimate mixtures of several minerals that it was almost impossible to distinguish the blue mineral from those intergrown with it, and quite impossible to secure a homogeneous sample for analysis. Some doubt was entertained as to the correctness of the identification of the material. In order to settle this question Mr. R. B. Gage recently sent a very fine specimen of this blue mineral from the Roebling collection to the Museum, with the permission of Col. Roebling to remove what was necessary of the material for an analysis. The results of the examination substantiate beyond a doubt the correctness of the original identification of this mineral as the blue cupriferous variety of vesuvianite, which has been given the varietal name cyprine. Since this is the first American occurrence of this variety and no complete description of the New Jersey material seems to be available, the results of the examination are set forth in some detail.