Picture of The Dark Nut

-- This fruit is so dark it s hard to take a picture without losing detail! I was intrigued by the look of this fruit which looks like a bull s horn. The supermarket has it listed as a Water Caltop but research on the net says a Caltop has four horns and a Singara Nut has two. Not sure if the market was wrong, but both these categories are supposed to be sweet tasting. The colors of these are purple to black.