Picked up this piece in a trade recently.
It is a bit unusual. You don't see these for sale often because
they are soluble in water and break down naturally in just a
few years. This piece has been soaked in mineral oil and I
will have to continue to soak it periodically if I want it to hang
around for any time.
Most of these crystals that you see are man-made, (very easy
to do), so I'm hoping this is the real thing. Reportedly from
an old copper prospect in Wisconsin. These crystals will
form on the inside of mines after there is room for them
to form, so this cluster may not be more than 10 or 20 years
old, if that. I really don't know how old they could possibly be.

But I love the color

Looks like that blue is jumping off the specimen it's so bright.  Reminds me of cavansite a little.