I cannot say that I have ever heard of a colour changing sapphire.. at least I did not before i found this beauty.
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"About Color Change Sapphire - History and Introduction
Color change sapphire is an exceptionally rare fancy variety of corundum which exhibits the unique ability to change color when viewed under different light sources. Although blue is the most common color, color change sapphire can occur in a range of other colors, including greenish, yellowish, pinkish and violet-purple, depending on the coloring agents within the specific stone. Typically, most color change sapphire shifts from blue under natural daylight to a violet-purple under incandescent light. Fine top grade color change sapphire can exhibit quite a noticeable and dramatic color change, but most material will only partially shift from blue to bluish-purple.
In order to truly appreciate color change sapphire, specimens should be observed under different lighting conditions, including early morning daylight, late afternoon daylight, fluorescent light and incandescent light. The unique and rare ability to color change occurs only in rare sapphire that forms with two light transmission windows rather than one. For example, a red gemstone appears red because it absorbs all frequencies of light except for red, but a gemstone that absorbs all frequencies of light except for blue and red appears blue when the light is rich in blue wavelengths, and red when the light source is rich in red wavelengths. Fluorescent light is rich in blue, whereas incandescent is rich in red. Natural daylight is well-balanced, which is why color change sapphire is best viewed under natural daylight."
[attachment 308095 IMG_0808.JPG]
[attachment 308096 IMG_0810.JPG]
"About Color Change Sapphire - History and Introduction
Color change sapphire is an exceptionally rare fancy variety of corundum which exhibits the unique ability to change color when viewed under different light sources. Although blue is the most common color, color change sapphire can occur in a range of other colors, including greenish, yellowish, pinkish and violet-purple, depending on the coloring agents within the specific stone. Typically, most color change sapphire shifts from blue under natural daylight to a violet-purple under incandescent light. Fine top grade color change sapphire can exhibit quite a noticeable and dramatic color change, but most material will only partially shift from blue to bluish-purple.
In order to truly appreciate color change sapphire, specimens should be observed under different lighting conditions, including early morning daylight, late afternoon daylight, fluorescent light and incandescent light. The unique and rare ability to color change occurs only in rare sapphire that forms with two light transmission windows rather than one. For example, a red gemstone appears red because it absorbs all frequencies of light except for red, but a gemstone that absorbs all frequencies of light except for blue and red appears blue when the light is rich in blue wavelengths, and red when the light source is rich in red wavelengths. Fluorescent light is rich in blue, whereas incandescent is rich in red. Natural daylight is well-balanced, which is why color change sapphire is best viewed under natural daylight."
