Rainbow Rays in Rainbow Lattice Sunstone
Figure 1. Parallel rays of golden, pink, and blue light were observed in this sample of rainbow lattice sunstone. Photomicrograph by Rosie Young; field of view 5.33 mm.
Figure 2. The changing direction of the rays is visible here when the stone is viewed through the same polished face but tilted to a slightly different orientation. Photomicrographs by Rosie Young; field of view 19.27 mm.
While examining a polished sample of Australian rainbow lattice sunstone, the author noticed a series of parallel “rays” illuminated with fiber-optic lighting (figure 1). These rays were initially considered some kind of internal structure within the feldspar. However, the orientation of the rays changed direction when the stone was tilted (figure 2). This indicated an optical effect whereby the fiber-optic light reflected off hematite inclusions and produced a ray of light corresponding to the color of the hematite platelet. This can be observed most easily in the upper right corner of figure 1. Extremely small particles within the sunstone likely allow the path of light to be visible, much like headlights shining through fog.
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