Tone - ✔✔lightness/darkness
Hue - ✔✔first impression, basic color
Saturation - ✔✔strength/intensity
Color Center - ✔✔defect in atomic structure
Gems best seen in Florescence lights - ✔✔Green Blue Violet
Gems best in candle light - ✔✔Red Orange Yellow
Color Zoning - ✔✔bands of diff color, variations in growth
Pleochroism - ✔✔shows different body colors from different directions
Dispersion - ✔✔separation of white light into spectral colors
Phenomenal - ✔✔crystal structures interaction with light
Opal is not.. - ✔✔a crystal
Moonstone - ✔✔alternating growth layers, adluarescenc
"Alexandria Effect" - ✔✔HUE depends on lighting