Appearance of double images of a gemstone facet junctions on the side opposite the viewer?

Appearance of double images of a gemstone facet junctions on the side opposite the viewer?

• A. Crystal Shape
• B. Crystal Systems
• C. Doubling
• D. Doubly Refractive

Answer: (C)

Doubling is the term for when you see two parallel images of a facet junction, observed by looking through the gem from the opposite side. This happens because the light paths inside the stone can produce two subtly offset images of the same edge, so the junction doesn’t appear as one line but as two. It’s an optical appearance tied to how light traverses and reflects within the facet arrangement, not a general property of the stone’s crystal system or shape. In contrast, describing the stone as doubly refractive would imply birefringence, which diamonds (being cubic) do not exhibit. So the observed double images are best described as doubling.

Doubling is the term for when you see two parallel images of a facet junction, observed by looking through the gem from the opposite side. This happens because the light paths inside the stone can produce two subtly offset images of the same edge, so the junction doesn’t appear as one line but as two. It’s an optical appearance tied to how light traverses and reflects within the facet arrangement, not a general property of the stone’s crystal system or shape. In contrast, describing the stone as doubly refractive would imply birefringence, which diamonds (being cubic) do not exhibit. So the observed double images are best described as doubling.