I purchased a gemstone purported to be Brazilian Amblygonite. It is the color of a light aquamarine. Under fluorescent light, it looks very light green. In daylight, it is a bright silvery blue. It is 0.46 ct, 6x4x2.7. Low RI = 1.628, High RI = 1.641. It exhibits weak dichroism, possible pleochroism showing a very light lavender-blue and light yellowish-blue (green isn't quite right). The difference is small. Under shortwave UV, the stone shows bright blue with an orange flash from some angles. Under LW UV, there is a very slight orange glow. No phosphorescence was noted.
The RI didn't give with my info on amblygonite -- but I have found many different sets of numbers for this. I thought I had apatite, but the fluorescence doesn't work. I haven't been able to find the dichroic colors for amblygonite, though the colors I found don't work for apatite. Ideas?