I've read and been told by a couple of sources that these stones are associated to the full moon (moonstone) and the new moon (labradorite).  They both are beautiful stones that reflect light and look very cool when moved in a light source.  The "rainbow moonstone" has a lot of color in it opposed to regular moonstone, and labradorite has much color in it.  These stones are used in jewelry and some people even leave their stones outside during their respective moon phases hoping to try to capture the moon's energy during their phases.  Any comments about these stones?  Do you collect them or use them for anything?  Beautiful stones for sure, if you haven't heard of them, you can quickly check them out on etsy.com or amazon.com.