The color of the color change garnets is primarily a function of the time of day, the type of lighting, and the chemistry of the stone. Light is measured by color temperature. Cool daylight above 5500K will highlight the blue or the green colors while warm daylight around 3500K will make the stones appear red. Some stones will be almost blue at 5500K while others will not become blue until 6200K and, every stone from every mine is different. 5500K is considered to be in the neutral daylight range while 6200K is already considered to be fluorescent.
Because early morning light is somewhat bluish in color and late afternoon light is reddish in quality, some color change garnets will be blue in the morning and red in the afternoon.
Candle light is the ideal incandescent light and it was from candle lights that color change in gemstones was first observed. Our photographers use daylight 5500K and incandescent lights 3300K to highlight the color change. A typical color change garnet shot will maximize the observable color change by obstructing any unintentional ambient light so that the resulting image is a function of a singular unmixed light source. Early morning light will make the stones look greenish or bluish while afternoon light will make them appear red.
Color change is also related to the distance of the light source from the stone as well as the angle of the light to the stone. For observing the red color, the penlight should be 2 to 3 inches from the stone and the strongest affect will occur if the light is directed across the table.
Real natural daylight is impractical for photography because of its variability. Please see the chart below which illustrates the point.
Temperature Typical Sources
1000K Candles; oil lamps
2000K Very early sunrise; low effect tungsten lamps
2500K Household light bulbs
3000K Studio lights, photo floods
4000K Clear flashbulbs
5000K Typical daylight; electronic flash
5500K The sun at noon 43.1656° N, Rochester, NY, USA
6000K Bright sunshine with clear sky
7000K Slightly overcast sky
8000K Hazy sky
9000K Open shade on clear day
10,000K Heavily overcast sky
11,000K Sunless blue skies
20,000K Open shade in mountains on a really clear day