I don't have any moissey but I've heard they don't reflect light like a diamond (doubly refractive) and won't really pass as one. If you have the money go for an Asha. If not do an Interlap (Winfields) in a RG or Chinese white color.

These stones from the UK are very nice. They all have lots of fire. I notice an odd swirling effect in the facet pattern around the edges of the rounds though (may be my old eyes), and the hearts and arrows aren't crisp and clean like a Winfields or Asha. They are great to look at size comparisons or for earrings or pendants. Some of the larger size stones- especially the 10 x 8 rectangular cushion have huge windows. The pears are almost indistinguishable from a Winfields. My regular 8mm cushion is close to a Winfields. As far as the color, mine all look very steely and not bluish at all. They are much better than a QVC type stone just not up to a Winfields. The 8mm tanzanite I got is VERY dark and not as nice as one I had from the shopping network. I think colors are hard to master and Interlap has had years to perfect their technique. I'm glad I ordered from them though. Unfortunately now I'm thinking I like the 2.5 ct size vs a 2 ct