Micro-World Gems & Gemology, Summer 2016, Vol. 52, No. 2

Aurora Iris Agate

Aurora effect in iris agate.
Figure 1. In transmitted light, this skillfully carved iris agate displays a scene reminiscent of an aurora. Photomicrograph by Nathan Renfro; field of view 5.28 mm.

When solar wind interacts with the earth’s magnetosphere, spectacular multicolor light shows occur. This phenomenon is referred to as an aurora borealis in the Northern Hemisphere and an aurora australis in the Southern Hemisphere. This author recently examined an iris agate that provided a microscopic scene remarkably similar to an aurora (figure 1). The 1.67 ct carving seen in figure 2 was fashioned by Falk Burger (Hard Works, Tucson, Arizona). Burger took advantage of this quartz’s unique growth texture by carving the agate’s back, producing a wispy iridescent effect that is visible when using a point light source. Along the lower portion of the gem was a thin layer of crystalline quartz with a seam of pyrolusite dendrites between the crystalline quartz and microcrystalline iris agate. The combination of these layers gives the viewer the impression of an aurora occurring over a forest-rimmed frozen lake (see video at www.gia.edu/gems-gemology/aurora-iris-agate-carving).

Front and back of iris agate.
Figure 2. The 1.67 ct iris agate, shown here in transmitted light (left) and reflected light (right) was carved to showcase the dynamic nature of the iridescent colors. Photos by Kevin Schumacher.

Nathan Renfro is the analytical manager of the gem identification department and analytical microscopist in the inclusion research department at GIA in Carlsbad, California.