I sometimes facet Danburite for my collector customers. Right now
the pale yellow variety from Madagascar seems to be in demand.
Usually, the more common color is colorless, and from Mexico or
toher locations. The hardness is around 7, the same as amethyst or
citrine, but the Refractive Index is about 1.63, so it cuts a
brighter stone than quartz. In fact, Danburite is known for its
exceptional transparency (or "water" as Riched Hughes calls it) and
cuys a very, very pretty stone when the angles are correct for the
design and the polish is well done with facets very flat. I like it,
it's very different....but I have never seen any with a green tinge.
I don't know the "value" or that there is a real established value,
but I can tell you that I get around $35-40/c for stones I cut
(fancy shapes) in the 7-12 carat range. Standard cuts like round,
plain emerald cut, etc., are less...it's really a matter of time
spent at the wheel for high precision, as the rough is inexpensive.
Hope that helps, enjoy your pretties!!