These are lovely semi precious gemstone Spectrolite cabochons.
The designer cabochons are an uninteresting feldspar that, due to minute inclusions, show an interesting display of beautiful iridescence or a flash of rainbow colors when light hits the stone cabochon in certain directions.
Spectrolite is a high grade variety of Labradorite. The difference between the two is Labradorite is usually a gray color, where Spectrolite is dark gray or black, giving a better background to make the colors pop more. Also Spectrolite cabochons display the whole spectrum of colors-hence the name.
Spectrolite comes from only one location, at Ylämaa in south-eastern Finland. It was discovered there while building in 1940 by the son of a Finnish Geologist, Aarne Laitakari.
This material was named "spectrolite" by the director of the Geological Survey of Finland.
The flash of rainbow colors occurs as you move the stone cabochon and when bright light hits it just right, making Spectrolite designer cabochons very difficult to photograph!