Refractive index: 1.66-1.68
Hardness: 6 to 7
Specific gravity: 3.17-3.21
Heat sensitive: Yes
Special care instructions: Avoid long exposure to sunlight and high temperature
Enhancements: Heat treatment
Kunzite is a variety of spodumene, which is a fairly common mineral, but the clear, pale pink to lilac ( and sometimes blue, green or yellow) colored form of it is much more rare to come by.
It was first found in California in 1902, and is named after the famous mineralogist George F. Kunz who first identified it.
Though it wasn't until the 1990's that this gemstone became a more mainstream gemstone, having been used only as a collectors gemstone prior to that time.
Kunzite is known for its strong pleochroism showing light or intense coloring in different directions.
For this reason, it is always cut to show the deepest pink color through the table of the stone.
As for most other gemstones, the deeper, darker, and more saturated colors of kunzite are considered to be the most valuable.
Most kunzite, in its natural form, is very light in color.
It is commonly heat-treated to intensify its color and remove brownish tones.
Kunzite may fade when regularly exposed to light, thus being called a "photochromic" mineral.
Some deep pink stones have turned nearly colorless from fading.
Although the color-fading effect is not this drastic in most kunzite, it is still important not to expose kunzite gems to strong light (especially sunlight) for long periods.
It is sometimes called "evening stone" for this reason.
The color of some kunzite can be restored or intensified by irradiation.
It will display intense color variations and color differences when viewed from the top and bottom.
It can even display multiple colors or appear colorless.
Notoriously known for its brittleness due to its perfect cleavage, these gems can represent a challenge for stone cutters.
Even though it has a decent hardness of 6 to 7, caution is advised when wearing kunzite adorned jewels, as sharp impacts can easily chip them.
Kunzite is trichroic, which means that three colors can be viewed from differing angles: pink, clear, and violet.
Sometimes the color change is limited to shade changes, such as from pale pink to dark pink.
However, when speaking of color changing gemstones, the ability to change color depends on the type of light.
A gemstone might look green in sunlight, but red in incandescent lighting.
Not quite the same thing, as pleochroism, which involves the same light, but different angles.
In conclusion: Kunzite is not a color-changing gemstone.