10.56 ct. Montana Rainbow Iris Agate

Color:  White Clarity:  Translucent
Origin:  Yellowstone River, Montana Cut:  Polished Slice
Treatments:  None Measurements:  23.9 x 21.7 x 2.2 mm

True Rainbow 'Iris' Agate is a rather astounding gem material that is quite rare in the market.  In normal reflected light, the stones look like simple Agate slices, however, once transmitted light is applied, they come alive with a full spectral display of color.  The finest material comes from the Yellowstone River in eastern Montana - even when a piece is found, however, it takes an experienced polisher to bring out the colors.  As the effect is caused by very thin bands within the Agate that diffract the light, the slice must be oriented in the exactly correct direction and cut to the correct thickness.  Any mis-step and the stone will not show the rainbow colors.

The quality of pieces varies widely - often there is just one thin band that 'rainbows' - here you get a nice series of bands that show the effect, both toward the top and bottom of the slice.  A great overall look, this is a scarce piece of a phenomenal US gem material.

$95 total