Well this is a very interesting stone and it has had lots of lore about it over the years.. There is an on-going debate on rather it was a for real stone or man made!
I have heard all types of stories over the last 20 years. My favorite was that it was fashioned from 100 years worth of layers of paint from the floor of an now defunct automobile factory in Motor City.. http://www.fordite.com/History.html
I'm sure that's not true but man I wish it was!
Until just recently I was sure it was man made after finding this: "Both the SSEF and GIA laboratories did extensive and in-depth advanced testing via both RAMAN spectroscopy as well as XRDF spectroscopy. They got the entire chemical breakdown of the material, Rainbow Calsilica. The results were a stew of man-made pigments, paraffin derived polymer , resin, calcite, and other components not “created” together in nature and some not created in nature at all."
But very recently I found a video that reports to have photos of the rough stone from a mine:
Video of the Rough: https://www.youtube.com/watch?v=V4rP9T1YW-Y
BUT that was another ruse.. this story is about it being from a tile factory.. I've heard that one too.
It's strange that no one really KNOWS for sure but whatever the verdict may be the controversy only adds to the attraction, mystique and value (is going up in value, now considered to be a good investment) of rainbow calsilica while making for an interesting conversation starter about your piece of jewelry!
This stuff is GORGEOUS and I have hoarded these (5) pieces for years. I have found this "stone", if good quality to be very expensive... these are excellent quality with clean bright colorful, distinct layers. Many pieces I have seen are mottled and just not nice, clean obvious layers. This is a good deal for 5 nice size pieces.
I had always planned on making a SW style sterling bracelet using these babies.. if you love them you should get them while they are listed. I hate listing them and will likely take them down and use them sometime when I get inspiration.
Dimensions of these are approx 1 inch for the long dimension.. please see photo with the penny in my hand for size reference.
PLEASE NOTE: Stones are very magnified in some of these pix. They are shot extremely close for detail.