Which term refers to the following definition: The appearance of double images of a gemstone's facet junctions?

Which term refers to the following definition: The appearance of double images of a gemstone's facet junctions?

• A. Doubling
• B. Doubly refractive (anisotropic)
• C. Dispersion
• D. Digging out

Answer: (A)

Doubling is the appearance of two images of a gemstone’s facet junctions. It happens because the stone is doubly refractive (anisotropic), meaning light splits into two rays that travel at different speeds through the crystal. When these two rays exit the gem, they can produce two slightly offset images of the same facet junction as you view it, especially under polarized light or with a dichroscope. The observable double image is the phenomenon described by the term doubling. The underlying property causing it is being doubly refractive, which is why that other term isn’t the exact description of the effect you see. Dispersion refers to color separation, and “digging out” isn’t a gemology term.

Doubling is the appearance of two images of a gemstone’s facet junctions. It happens because the stone is doubly refractive (anisotropic), meaning light splits into two rays that travel at different speeds through the crystal. When these two rays exit the gem, they can produce two slightly offset images of the same facet junction as you view it, especially under polarized light or with a dichroscope. The observable double image is the phenomenon described by the term doubling. The underlying property causing it is being doubly refractive, which is why that other term isn’t the exact description of the effect you see. Dispersion refers to color separation, and “digging out” isn’t a gemology term.