So this is another question about distinctions between two cultivars, one modestly priced, and the other somewhat pricey. They look very similar in pics, but I have not seen the Black Truffle in a pic displaying iridescense, nor do the seller listings mention it, while this is a big selling point for the Black Mamba, and some other 'velvet' varieties. I'm just wondering who has experience with these, and is this an accurate distinction?